Anything that you can prep ahead of time and portion and package like hummus, baba ganouj, different dips, veggie pates etc can be sold with house made pita chips. Easily made and holds great. Soups- hot when its cold, cold when its hot. Loads of different salads, noodle salads, pasta salads etc. Wraps are also easy to have pre-made as a grab and go. Any kind of cookie or easy dessert is also good.
Good luck whatever you do!