Potato skins are easy and fairly inexpensive. Bake plenty of potatoes, cool, cut in quarters. Scoop out most of the potato, leaving the skin with a fairly thin layer of potato. Drizzle with olive oil and bake in a hot oven for just a few minutes until the skin crisps up and the potato layer becomes slightly golden. You can bake the potatoes and quarter them well ahead of time, and then do the final crisping when the girls are ready to eat.
Have lots of toppings: black olives, green onions, cooked crumbled bacon, shredded cheeses, sour cream, etc, and let each girl top her own potato skins.
Then save all the potato that you scooped out (and the extra toppings) and make a baked potato soup for your family the next day (look up the Hard Rock Cafe potato soup recipe online - it's excellent).
Brownies are delicious, especially with this method: bake brownies as usual (from a mix, or from scratch). Then when they're done, remove them from the oven and immediately spread unwrapped York peppermint patties all over the top (cover the top of the brownies). Return to the oven for just about 2 or 3 minutes until the peppermint patties start to soften. You don't want them to melt, just soften and collapse a little. Remove from the oven and use a spatula or knife to spread the softened patties like frosting.
And since they're dancers, they may want to eat healthy, so have a nice big tray of fruits available: grapes, strawberries, blackberries, raspberries, etc, and healthy crackers. Perhaps cubes of cheese as well. Make it look attractive!
Or bake mini meatballs, and then transfer them to a slow cooker to stay warm. Provide marinara sauce for dipping, or BBQ sauce, or teriyaki sauce. Serve with warm rolls and raw vegetables such as carrot sticks and celery sticks and broccoli florets.
Make sure to inquire whether any of the girls has an allergy or food intolerance.