I understand the basis for your wish to reward the students for doing the right thing and I know you're only considering doing so from a purely genuine, helpful stance.

BUT....................................don't.

Don't attempt to sublimate that awesome feeling of accomplishment they'll
receive by giving to the victims in your community. A reward or prize only serves to marginalizes the act of participating in charitable works.

Do the students a wonderful service and let the satisfaction received from being budding philanthropists be their reward.

I am the president at an elementary school in Antioch, TN. We recently had a devastating flood. Our community has really come together to help those in need. I am really proud to be a part of it. Our school decided to have a coin drive. We have students that are giving up their snack money to help. I would like to reward all the children for their wonderful spirit. I know that giving is a reward in itself, but I really would like to give them something extra. All ideas are welcome!!