I do each event as a seperate operation. My flyer indicates all the food I can do and further indicates that every event is different and unique, "call for pricing". Let’s me charge more for the banks and corporations in the area, but less for the home parties and non-profits. I have no minimum because every event could be a winner, even if just in contacts. At the end of the day, 200 bucks is 200 bucks I didn’t have little while ago.
I do like the all you can eat option, though. That may go on the catering menu as an option, but again, without a set price.