I did a deer widown crop a few years ago and all our proceeds went to The Humane Society.
What we did was ask some of the bigger scrapbooking companies for donations (not sure how your time limit is). We called grocery stores and explained what we were doing, most of them were more then happy to donate. We got all the items donated for a spagetti dinner, WM gave us a $50 gift cert. and we used that towards drinks. ANd then our local LSS let us have stuff on consignment. If it sold, we could keep a percentage of it if it didn't we just brought it back. ANd they let us use the tools that they have there for crops.
But we put on all the flyers that we advertised, for people to bring their own trimmer and supplies if they had them. And most people brought snacks and stuff...
Hope you have a good turnout and do well!!