It is called a pledge drive...........I personally have never done one, but have read about them. Typically a "pledge card" is sent home with each child or mailed to their house. Let them know that their contribution is tax deductible, and that generous giving frees families up for family time, and not time spent selling stuff.
If you look at parachiol (sp?) school websites you will probably come up with a pedge card format you can follow, and just change it to reflect your school.
I am looking for info about a fundraiser that does not include selling things. Basically just looking for a letter or form to send home to parents letting them know that we won't be selling anything; we would like the parents to donate money instead.