S.C.
Is this a wading pool party?? If so, cute idea!!!
I agree with the "keep it simple" theme. You will have a difficult time finding compatible food for toddlers and adults. Have simple foods for the kids---mac & cheese, cut-up melon, homemade chicken nuggets that you make ahead of time. You can rent small chafers to keep the pasta hot from a party rental company pretty inexpensively. You could partially pre-cook chicken breasts (buy the bags of boneless, skinless at Costco) ahead of time, then finish them on the grill at the party. Serve them as grilled sandwiches with lettuce, tomatoes, pesto mayo, sauteed onions (can be made 2-3 days ahead), a fresh pasta salad (you can also make that the day ahead), a fruit bowl (the kids can eat that), maybe some baked beans. Everything can be prepared ahead of time, set up your buffet the day ahead as well so that you'll know where exactly you'll place everything when it's time to serve. Have your salad, pesto mayo, etc. in a covered bowl in fridge, so all you need to do is take it out and put it on the table at serving time. Set up a small bar on a table outside and try to keep the food inside so you don't have to worry about flies. Keep it simple and save the big bucks for parties where she cares and knows what's going on!!