The kids eating is not a big problem.  They are FH's kids and he can manage.  As Petro said, you two have far bigger issues, including money and his parenting.  Will he be supporting these kids for years?  Many parents pay for college and first cars.  Even if he makes a lot of money, this can be very expensive.

What do kids eat is my biggest issue.

Trust me, that is NOT your biggest issue. You have no idea how their family dynamic works, you have only met 2 of the 4 kids, and barely know the 2 you have met. You have no idea how your BF parents, how this will affect you, financially, and you are underestimating how miserable a grudge-holding daughter and spiteful BM can make your life.

Just scared about a lot of things

And you should be, as it sounds like you truly don't know what you're getting into. How long have you been with this guy?

this is where my happiness comes from

That's what you think, now, because you have been sheltered from the reality of the situation, you have been dating your BF in a bubble. It seems that he has kept you separate from his family life, so again, you have no idea how life, real life, with him will be.

People can hide who they really are, what their life is really like, for quite awhile. It's called "bait and switch" and it's quite common when kids and an ex is involved. I would not even move in with him until you know him better, as a father and as BM's ex husband. He agreed to put off the divorce because that's what BM wanted? What else is he willing to do to appease BM? His kids? How much does he expect YOU to sacrifice for HIS family?

How old, exactly, are the kids?  From what you've written, it sounds like there's a 20 year old, a 16 year old, a preteen and one more who has to be at least 5, probably much older than that.  They seem old enough that you shouldn't have to worry about what kids eat. Teen boys eat everything that's not nailed down. Properly raised children, especially older ones, should be eating the same meals the adults eat.  This is NOT a problem, let alone your biggest problem.

I would suggest going very slowly, and not making difficult to reverse moves until you really get the lay of the land. You are negotiating a land mine here, and I'm not sure you even realize it.

"...my mom wants me to follow in her footsteps and not get involved, stay single and independant. Too late, this is where my happiness comes from."

Listen to the person who loves you the most in this world - your mother.  She is obviously seeing things that are deeply troubling to her about your significant other/relationship, but she is probably reluctant to say it outright to you.   You are wrong not to honestly listen to her wisdom and concern for you.  

Secondly, this man (and his extremely overloaded baggage) is NOT where your happiness comes from and it is NOT too late to turn away from this mess.  The fact he is looking for full custody of two of the kids shows he may be more interested in a housekeeper/nanny than a true life companion.  Perhaps you know this, too, because your concerns over a minor thing like "feeding" the kids shows that he has already given you an impression (overtly or covertly) that you will be expected to do the heavy lifting in managing the household and taking care of HIS kids, instead of him doing it himself.  

And a mess it is.  I will tell you after 15 years in a stepdaughter situation, that if she does not accept you now she never will.  In fact, she will probably do all she can to make your life miserable - everything from direct confrontation to complete exclusion.  And it isn't something that many of them grow out of or change over time.  I'm 15 years in and the needle of "acceptance" from my SD (nearing 30 years old) still hasn't moved an inch no matter what I did or didn't do.  It will always be a source of friction in my relationship with SO and I figured that out early on.  That's why I didn't, and won't ever, marry him.   Read these forums - you will see the vast majority of problems come from stepdaughters.  To compound matters, you haven't even met 2 of the 4 kids, and yet you think this relationship is where your happiness lies??

Third, you have a BM who is bad-mouthing you and will continue to do so.  This sounds like a dramatic, high-conflict divorce which is just now in its final stages.  Doesn't matter if it's been years in the making, the fact is they are just now divorcing.   There has been no time for your SO to even gain his emotional breath or have closure on his (failed) marriage and yet he's already entered into a serious relationship with you, which was not wise on his part.  Furthermore, his son who seems to show affection for you will soon start getting the brunt of BM's anger, as she will no doubt become very jealous if he indicates he likes you.  She will begin the mind games with him and put him in a loyalty bind with her.  So this young kid may wind up being psychologically punished by his mother because he DARED to show an interest/like in you.  If you care for this boy at all, you must consider these consequences.   

Last but not least, if you enter into any kind of financial transaction with this man (buying a house, etc.) or worse, get pregnant by him, you are asking for a great deal of legal problems and life-long heartache.  

Listen to your mother.  She has your best interests at heart and can see things more clearly than you are able to.  

that's clearly written on the wall.

Let me say that I, and other ladies here on this forum may seem like pessimists by nature, however, we have lived "IT" and know all too well what lies in store. These men take angelic women with wonderful intentions and aspirations and kill who we once were with their actions and lack of needed action. Through our realities we are able to give sound advice, just as the previous poster's have responded. Nobody ever thinks it will be their reality. They think, "My love will be enough and I will fill all his voids with my love." Wrong. They take pieces out of you and keep on going, pillaging through life and doing exactly what their kids want them to do. You aren't even on the totem pole.

When love is new, and fun and exciting we see only what we choose to see. I think most, if not all of us married because we loved a man, and we diligently tried to be loving and kind to all that he loved because it mattered to HIM. Nobody enters into marriage thinking it could ever be a hell on earth. That being said, you are seeing a "great man who loves his kids, and appeases his soon to be ex," in your case. It looks and feels endearing. As time rocks along, like many of us have experienced, you will see BM will turn her tribe against you. There will be angst for years to come over the most petty things, which you will be blamed for. In turn, you will take your seat in the same chair we all have. You will be the whipping post, and heaven forbid if you voice your thoughts, ideas and opinions about how he parents(or doesn't parent), responds to his ex and so forth. Many of us have had ADULT (so-called, adult by years, not mentally) Step-offspring rise up against us, for no reason and completely unprovoked,  IN FRONT OF OUR DH'S WITHOUT SO MUCH AS A WORD BEING SAID TO REPRIMAND THEM OR REIGN THEM IN ON THEIR HORRIBLE BEHAVIORS. Later we learn that DH has colluded with his genetic mess, about us, due to divorced daddy guilt, and to try to win their favors. All the while smiling to our faces, professing their love for us and allowing us to cook, clean up after and use our valuable time, energy and kindness to shop for their birthdays, Christmas, etc. We, meanwhile are very unsuspecting, because WE THINK THEY MARRIED US FOR THE SAME REASONS WE MARRIED THEM:Love. 

Ex's NEVER fade away. Even when the kids grow up. You will grow to resent the fact that he had kids with her, and is forever tied to her through their procreations. You will bear the burden of this sad, and undeniable fact for the duration of your marriage. Throw in your own bioligical child, and watch the fangs come out from the ex and her kids.

Think this through. You are in your EARLY 30'S WITH ZERO BAGGAGE. You are about to step on an emotional trip wire that you may never recover from. Please, seek out a man who is more your equal, not one who will swallow you up with life's responsibilities and have little to no appreciation for you and your efforts and talents. 

Also, I always recommend "new to the site" ladies flip over to the Adult Step section and search your topic specifically. There's a reason it is the most traveled sub-topic here, with over 77,000(+) posts from troubled ladies. We are trying to help you dodge an emotional bullet here. AA has NOTHING ON STEP-LIFE. Believe me, there is NO 12 STEPPING THIS AWAY.

Please, put heavy stock into your mother's advice. She only has your best interest at heart. As a mother, I always encouraged my kids to find a similar match in life. Not one who is saddled with so much baggage you will never know joy for the rest of your days. Thankfully, they have listened!

I wish you wisdom, joy and peace as you navigate through these emotional waters.

Oh my dear, you are really in for a surprise. I hope you stick around here and keep us posted along your journey.

Why would you want to be fully cooperative with his EX? A word of advice....all that means is that BM will RULE your house and  your future husband until the day she dies....do NOT do that. Set boundaries right NOW....BM is not the boss of one single thing in your home...ever. She will hate your guts...ignore her and all of her actions...she is irrelevant to you. Make sure your future hubby is NOT at her beck and call if he is afraid of her...if he bows down to her...if he makes decisions with her about his home or about you...run like hell as far away as you can and do not ever look back.

Since you only asked for advice on what kids eat, I'll refrain from any other words of wisdom. Kids are just like adults regarding eating habits.  They have their own individual tastes and what one kids eats another may hate.  In my own extended family, one little prefers veggies and fruits to meats and sweets while another is a meat and potatoes style eater and the youngest is into peanut butter and honey sandwiches.  It sounds like you feel you can talk to these kids; why not ask them what they like?  When you spend time with them, what do they eat?  Do they ever ask for a specific type of food?  If you have no idea, then maybe you need to pump the brakes and slow things down until you've gotten to know the lay of the land better.  Well, dang! I guess I offered unsolicited advice after all.

To answer the what do kids eat question......you will quickly learn that is a loaded question.

My 4 kids (including a 1 year old) eat what I put in front of them...always have. I cook dinner...they eat. Period. End of Story.

Now on to skids 12 and 16...they eat whatever they want which is usually chips, french fries or chicken nuggets. If by chance they eat a real meal it has to be plain noodles or ham and bread...no not a ham sandwhich b/c that is gross...just a ham on one part of the plate and a piece of bread on another part of the plate. Why do they do this? For attention I think....SD12 has to be different and has some weird obsession with not eating or having to have her own personalized separate meal....they don't eat real food....ever....b/c it's "gross". Do you know how weird it is to go out to dinner with a middle schooler and a  highschooler who both ask for the kids menu and order chicken nuggets and fries no matter where we are........and if they don't accept the restaurant that DH and I chose...they just refuse to order anything.

They will eat, what ever he cooks.  You have bigger problem.

He is keeping the kids from you,  There must be a reason for that.  You already know the two older ones don’t like you , or there father dating. You are taking there money.  Older SK need massive amounts of money.  College, cars, wedding   Who is paying for that, and what amounts of money must be settled in writing before you go any further in your relationship.  

Histoty get rewritten if not in writing.  You must meet and spend time with SK,  remember you may have SK 12/7/365. It’s onlt one BM accident away.  Or BM running off with a new BF. Who doesn’t want SK 

happiness”, trust me that if you will do everything for their happiness, you will be miserable, resentful and angry.

you should be doing what makes you happy, bending over backwards for future skids who want nothing to do with you, who as a result of bio mums brainwashing and project “destroy exhubby and relationship with his kids” will likely spew all her hatred and lies, actually its pretty much guaranteed 

bio mum refused to tell kids they’re separated and finaliZing a divorce, its pretty much common sense if they have lived apart for yrs that they were headed for divorce.

bio mum refused to finalise the divorce because she isn’t done taunting your partner and dishing out the maximum pain possible.

from what you’ve posted, the exwife has not been cooperative at all, so why should you bend over backwards to be fully coooerative for her.

you seem to be dealing with a narcissist, her mission is to toy you like a puppet. She may demand you bend over backwards for her kids like they’re the centre of the whole universe for everyone when they’re not, she will push them on you to deal with because she wants to chill from being a mum but then continues to trash talk you.

all that should ever be expected is basic civility and if they’re disrespectful, you get to disengage and not give a stuff and she can’t do anything about that...

kids eat what their parents cook for them. Unless they have allergies, whatever healthy food you cook is what they eat. They wanna chuck a hissy fit, fine they go to bed hungry

You sound like nice person. And I do agree with people who have said to listen to your mom. 

I’m sorry to say this because you probably love this man, but I think you should get out of this situation now while you can.

I suggest you continue to live separately until the divorce is final, he has custody of the kids, and you can evaluate how he parents and how (if) he prioritizes his relationship with you.  
You're WAY ahead of yourself worrying about what kids eat. It's their Dad's responsibility anyway.
Let us know what happens. 

Don't over complicate right out of the gate. First, kids eat what they are served. End of discussion.

Next, do not do anything with his X other than keep her the hell out of your marriage.  Period.  She gets no say in anything in your marriage or home including how you and your SO partner and parent in your home.

Now for the big one. Kids are not respected unless they earn it with compliance with behavioral and performance standards.  If they comply, they get respect commensurate with their performance. If not... they suffer escalating consequences that deliver an escalating state of abject misery until they do comply.

The key to a successful marriage is no mystery.  Both spouses must put each other and the marriage as the sole top priority.  Nothing takes priority over the marriage. Period. Including children. Children are the top relationship responsibility but never take priority over the marriage or the partners to each other.

Neither is the key to successful parenting a mystery.  You and your SO set the standards of behavior and kid performance in y our home and family.  Then enforce those standards.  

You are taking on what is by all indicators a nightmare.  A man who is still married.  His toxic not yet XW, his several children, and all of the baggage, angst and drama that all represents.

I recommend that you listen to your mother.  You are young. There are countless men out there that are your age (give or take a few years), accomplished, and without baggage.  Either stay single and enjoy your life or have the self worth and confidence to not settle for anyone in your life who is not completely and entirely focused on you and making a life with you without the distractions of a lifetime of shitty decisions and all of the associated baggage.  Find a partner who will build a life with you together as equity life partners and not require that you sacrifice yourself and your young and unfolding life to his life and baggage.

Good luck.