some suggestions:
1) wanna try satay? probably 20-25cents for uncooked sticks. you can order ketupat together. since they also come with cucumber and onions, these can kinda take care of the salad part. also the ketupat is something like rice, thus filling.
2) otak otak sticks? these can be eaten with bread, thus again filling enough to last through the nite. growing boys and girls need energy food to jam rite?
these 2 above mentioned items no need seasonings, so less leceh.
3) of course the usual chicken wings and various chicken parts.
4) usual finger food stuff, eg. nuggets, hotdogs, etc.
5) salads or fruits. these can be prepared at home.
6) can also consider getting the indian or muslim food stall to fry mee-goreng or bee-hoon.
5) don't forget marshmallows?!!
6) for drinks, if can get those drink containers, can make own drinks cheaper, cos it's just a bottle or two of syrup water and ice. otherwise getting pre-packed yeohiapseng kinds are more expensive though less troublesome.
one last thing to mention, since the surroundings are gonna be less than bright, if you serve fish, is it ok because of the bones?