I went to a recent crop where they served yummy chicken salad with croissants for lunch. You could also do a cold cut tray with meat and cheese and let them build their own croissants.
Good snacks include most finger foods:
brownies, cookies, snack mix, candies, bite-sized fruit pieces with toothpicks, relish plate, ritz bits, pretzels, etc. I think potato chips tend to be a little greasy for a crop, but baked tortilla chips are a good choice esp. if there is a taco dip to go with them.
I always love it when drinks are offered. Something cold helps keep me energized! Iced tea or lemonade is a good choice, since they are inexpensive and most people like them. I hate to attend an all day crop and have to go in search of a jumbo drink to stay awake.