There was a crockpot mac & cheese recipe floating around Facebook that a lot of my friends with little kids said was great. I know it involved butter and a brick of cream cheese plus cheddar. You can probably find it on line. I see others on line that include the cheddar cheese soup and eggs, with some reviews that say the eggs didn't hold up well over time.
I'd be surprised if the kids didn't eat it - you could always leave an empty box of the Kraft stuff on the counter and fool them!
I make a "grown up" mac and cheese with white sauce, Fontina and Parmesan cheese with whole wheat pasta, topped with buttered bread crumbs and wheat germ, and do it in a casserole dish - it works out great. I make it ahead and just reheat it, but if I can't bake ahead, I just make the pasta and coat it with some butter so it doesn't stick, pre-grate the cheese, and pre-make the white sauce, refrigerate it all, then quickly assemble it in 2-3 layers just before baking. I think if you use real cheese, it keeps fine - not sure about the processed cheese in the box. I suppose you could experiment ahead of time.