Hey 3156
First off, welcome to CD and FIRST.
Definitely follow RC's advice about the movie theater demo. It is a sustainable fundraiser that can be done every year and multiple times a year at a very low overhead cost. Team 11 and 1323 both do these types of events and it raises quite the penny.
Quick fundraisers are the best in times of quick profit needs: carwashes, bake sales, pizza sales at school (sell a slice for 1.50 at the end of the school day). In a school of about 1300 kids we go through 10-12 pies of pizza per day. And that's just plain pizza! :O
PM me for more help. Good luck this season, I know you guys will do great.