Lisa,
Sounds like a great idea could you give more info.
You said they come in and "work" do you mean volunteer at a specific event?

Did you guys know that McDonald's does a fundraiser for schools? They allow the staff to come in on a night for a few hours and "work". The school gets 10% of the hours sales. We just did it for the second year in a row and we made $500! Just an FYI.