Helpful hints/thought:
Make sure your teachers let you know about how much time each projects take so the people signing up with have enough time for all their crafts and you wont be there all day.
We let people sign up for however many projects they think they can finish that morning. I would put a limit on how many of one project someone can sign up for though. We had someone sign up to make 26 of something once. If the project doesn't have a lot of prep work it's fine but if it does then make sure to put a limit on it. My recommendation is around 8.
We had a no refunds policy. This is because if the teachers already bought the supplies then they are out money if they decide you don't want to do it or can't make it and want their money back. I have offered to make kits with some of the supplies if people told me they couldn't make it because something came up.