Salad bar. Kids love the different dishes and being able to pick and choose. And kids love to dip anything - so serve baby carrots (or cut big carrots into smaller sticks), celery sticks, grape tomatoes, pepper slices, cucumber spears or discs, and a little dressing on the side (ranch is a favorite). You can do "make your own" pizzas with the small Boboli crusts or let a couple of kids split a large pizza crust and make their own half - put on the sauce, then offer peppers, defrosted chopped spinach, maybe some onions, grated cheese, sliced meatballs (just defrost the cooked turkey meatballs and slice them), sliced mushrooms (okay, I know, few kids will eat them but the adults will), and any other toppings you like. If you put enough choices out, everyone will find something they like and probably choose more items than they would if they are all mixed. Again, make an assembly line on the table and let people move along and create their own. You hardly have to wash the bowls the stuff is in - just rinse and drain! Use a popsicle stick or craft stick with the person's name written in a sharpie marker, then stick that under the edge of the crust so when they come out of the oven you know what's what.
You could also make a mac & cheese casserole ahead of time, or do some healthy chicken nuggets ahead. I use chicken breasts or tenders, cut them up in nugget-sized pieces, dip in beaten egg, and then dip in a mix of whole wheat bread crumbs and wheat germ. I quick-fry in a little olive or canola oil to crisp up one side, then flip to do the other side. As they are crisping, I remove them with a spatula and put them on a baking sheet. When all are done, I finish in the oven at 350 for about 10-15 minutes. Serve with dipping sauces (ketchup or marinara, mustard, etc.).
I'm not a big lover of hot dogs, but for feeding a crowd, it's very easy to buy cocktail franks (regular or all-beef) or even cut up regular hot dogs. Get some crescent roll tubes in the dairy section, and open/unroll. Take each crescent and cut it into about 4 pieces, making sure all are sort of triangular in shape (just wing it - they won't all be the same). Lay a cocktail frank at the wide end of the triangle, and roll toward the pointy end. Set them all on a lightly greased baking sheet and bake according to the crescent roll directions until lightly browned. Serve plain but with dipping sauces (yellow mustard, dark spicy mustard, ketchup or other tomato-y sauce). They are easy to pick up because of the dough (and not too hot for little fingers), and people can eat what they want.
Serve crudites (carrots, celery, peppers, cukes, trimmed green beans, snow pea pods, broccoli florets, cauliflower florets, grape tomatoes, zucchini spears, you name it) on the side and everyone will get some veggies and you will feel you've given them a balanced meal!