Depends on if you mind sharing and if you want table service meals or quick-service.
For table service, look for buffets for the best value over all.
Some great values for sharing:
Cosmic ray's counter service at MK...chicken and ribs combo is more than enough to share.
dole whips at aloha island and funnel cakes at sleepy hollow are reasonable treats.
Pecos bills in MK also has a new fried chicken dinner with potatoes and corn and they have a fixin's bar there with sauteed onions and mushrooms and basically a mini salad bar. You can really stretch a meal there with adding from the fixin's bar.
EPCOT-morocco counter service has a chicken platter that is easily shared.
in the back of France there is a pastry shop with reasonable pastries and ham and cheese croisants.
the mexican cantina outdoors also has reasonable combo meals.
At downtown disney, Wolfgang puck express has HUGE meals that are easily shared.
Earl of sandwich has DELICIOUS sandwiches and salads and wraps for about $6.
Goofy's candy company has make your own treats for a couple dollars...fun treat!
There is a list of restaurants with options and prices available here:
http://allears.net/menu/menus.htm
hope that helps you plan a bit.
Don't worry about any MUST-DO dining unless your kids are interested in a certain character meal. The food at Disney, for the most part, has become mass produced due to the popularity of the dining plan. So, the quality pretty much everywhere is about the same as a T.G.I fridays (with a few exceptions that are better or worse).
Just keep in mind that your best bet is to stick to counter service meals and to share often. Meals at CS are huge. You can always get a snack or something else later if you need it.