Grill chicken (more than for one meal)..preferably chicken breasts.
Slice it as you need it.
You can put it on top of a salad: grilled chicken salad (and kids usually love to munch fresh raw veggies with a little ranch dressing...so leave the ingredients of the salad separate on their plate--that's what I did anyway) lettuce, a couple of slices of red bell, cucumber, black olives, etc
You can roll it up in a tortilla with whatever you like (lettuce, cheese, salsa, avocado, etc) and have chicken wraps.
You can dice it and throw it into a quesadilla on the stove: at first my kids liked just chicken and cheese. Now they like the peppers and onions, too. with salsa and sour cream on the side.
Dice it and mix it up into chicken salad (with diced sweet onion, diced red grapes, dice red delicious apple and maybe a little celery, dollop of mayo). Serve in sandwiches or on top of lettuce with wheat crackers on the side.
Then there is always the ground beef. The easiest one I know is a lb. of beef, 1 jar of your fav salsa, 2 cups of shredded cheese: brown the ground beef in a skillet, drain off grease, mix in shredded cheese till melting and stir in salsa. heat and serve. Put it in a burger bun if you want. Or roll it up in a tortilla.