Dried beans. I've heard it said that beans are the poor man's protein, but poor or not I just love them. Just about any kind is good. Throw in the crockpot with some spices and stock or water. You can add meat like chicken or sausage if you like. Serve with a bread and salad. So delicious and very inexpensive.
I don't love beans but I like them just fine, and make a lot of them pretty much as Bamagirl does, only I usually add smoked ham hocks or a smoked turkey leg (which are sometimes too big for my 3 qt crockpot!).
thanks so much for the awesome suggestions everyone. Yes we do eat out a lot of fast food, unfortunately. Trying to curb that for both health and my pocket

Love the idea of breakfast for dinner! My kids LOVE eggs and pancakes and bacon. Unfortunately I lent my slow cooker to my friend and never got it back because she broke it

so no help there.
One of the downsides to fast food is that it doesn't do much to teach kids to appreciate a broad range of foods. Going from a fast food diet to the way we eat all the time would be a shock to any one's system, but it's even harder on kids who've always eaten that way. I think recipes that depend on a lot on similar flavors make the transition easier, like this one (which I quadruple for my troops!):
Burger Bean Bake
2 slices bacon, cut into 1-inch pieces
1/2 lb. ground beef
1/4 cup chopped onion
8.25-oz can Green Beans, drained (or use frozen)’
8-oz. can baked beans
8-oz. can kidney beans, drained
1/4 cup ketchup
1 tsp ground mustard
2 Tbs molasses
1/2 tsp Worcestershire sauce
Heat oven to 350 degrees F. In medium skillet, brown bacon, ground beef and onion; drain. Add all remaining ingredients; mix well. Pour into ungreased 1-qt casserole. Cover; bake at 350 degrees F for 30 minutes or until bubbly.
3 (1-cup) servings
(can also microwave)
Even my supposed bean-hating kids like them that way.

Another way most of them will eat beans is this one (we double it, put it in a greased 9x13" pan, and bake for closer to 30 minutes):
Easy Mexican Pan Bread
1/2 cup dry beans (or one 16 oz can beans -- save the liquid!)
2 Tbs oil for sautéing plus 2 Tbs more
1 large onion, chopped
2 cloves garlic, minced
1 egg, beaten
1 cup cornmeal
1 tsp baking powder
1 Tbs chili powder (or to taste)
1/2 tsp ground cumin
1 green pepper, diced (optional)
1/2 tsp salt
1/3 cup (or considerably more) grated Monterey jack or other cheese
1/4 cup sliced black olives (we do half with and half without)
Garnish; chopped fresh onion and/or tomato
Cook beans with extra water; drain, reserving 3/4 cup of the cooking liquid. Preheat oven to 350 degrees F. (Or use one 16 oz can beans - go easy on salt.)
Heat oil in an ovenproof 12” skillet and sauté onion and garlic until onion is translucent. Remove half the onion and garlic to a bowl and add the cooked beans and reserved liquid, egg, 2 Tbs oil, cornmeal, baking powder, chili powder, cumin, green pepper, and salt. Mix well, then return to the skillet, but do not stir - the onion should stay on the bottom. Bake for about 15 minutes. Just before it is done, sprinkle with grated cheese and olives, and continue baking until the cheese melts. Garnish before serving.
6 servings
My kids like to have stuff on hand so they can "scavenge"; the choices change depending on what's on sale, but someone gave a list earlier that covers most of them.
One thing not on that list was ramen noodles or "Cheese Ramen" -- cook the ramen noodles according to the package directions, add the salt packet to taste (I cut mine back a good bit for cheese ramen), lift the noodles into your bowl, lay a slice of American cheese on them (or in the midst of them as you pull them out), pour the hot broth over so the cheese melts a bit. The kids like cheese ramen, but it's definitely not health food.
My kids have no idea what "breakfast food" is all about -- they do have cereal for breakfast once in a while, but breakfasts around here are more commonly left overs or regular food. Friday nights we often have pancakes -- regular pancakes, mostly, but also ginger pancakes with lemon sauce, or pumpkin pancakes with spiced syrup, ricotta pancakes with jam, etc. Eggy puffed pancakes, the kind that sink in the middle, baked in a cast iron skillet (traditional) or a 10" cake pan (works fine) with fruit in the middle are fun, too, but a bit more hassle for larger families.
Older cookbooks, like the Betty Crocker cookbook from 1956 or 1971, will often have a ton of egg recipes, ranging from basic creamed eggs and eggs goldenrod to elaborate baked dishes, most of which are pretty economical.