I am sponsoring an eight hour fundraiser crop for the Avon Walk for Breast Cancer in Memory of a fellow CMC and dear friend, who past away last month.
To start with, I think getting the word out that you are having a fundraising crop is important. Many people who prefer to crop at home on their own, will participate for a worthy cause.
For our crop, each person who comes will get a goody bag of product. We will also be doing raffles throughout the day of both CM products and Breast Cancer awareness items, ie mug w/ beanie bear, the pink ribbon socks, etc. I don't want to reveal too many items, one of my attendees frequents this board.

We will also have new technique demonstrations.
I have found though at my regular monthly crops, people are primarily there to work on their albums and to eat. Needless to say we will have lots of chocolate. I am toying with the idea of a chocolate fountain fondue.

So give them lots of cropping space; about three to a round table, four to six to two rectangle tables put together, good food, and a little music. The group will have fun.
Good luck with your fundraiser. I know how much the success of our fundraising crops means to us.