Hi Melanie!
Magic Kingdom is a "must" in my opinion! There is so much to enjoy there, even with little ones, that you might find you need a second day to go at a pace where you can really take in all the magic! There are seven lands to explore and attractions and show that bring out the kids in even the adults! If you're worried about which attractions are good for the little ones, there's a pdf
here, "Attraction Height Requirements" where the rides with height requirements are listed and anything left off the list can be enjoyed by guests of any height.
Dining at Walt Disney World is a vacation experience in itself. There are quick counter service places to grab a quick bite and there are restaurants that range from casual dining, to character dining, to fine and signature dining, and even dinner shows.
I would suggest a character dining experience with the little ones because it gives you time to slow down and recharge while having a delicious meal, and your kids will get a chance to not only spend a little more time with characters, but they'll also get a chance to warm up to them if they are a little shy of characters. Crystal Palace has been a family favorite at Magic Kingdom.
Also, the fine dining is worth experiencing. Plenty of the restaurants welcome families, so don't be afraid to try one out if you're worried about bringing the kids along. Citricos at the Grand Floridian Resort is a recent favorite of mine.
Restaurants are located in the theme parks, at resorts, and even at Downtown Disney and the Boardwalk. You can search through all the options
here.
Come back to the Moms Panel if you need any more help planning your magical vacation!