Hey Rick,
Howzit man. So a question. What are your regular prices? I tend to use those as a guide for how much to charge. I usually have a minimum. Say 100 people at $5 a head. I can count buns at the end of the day, if I go over the 100 minimum then we start adding $5 per. Or something like that. But my products are a little on the pricey side regularly. Now that $5 would get people drinks and chips as well, if they only wanted dogs I would subtract a dollar and do a minimum of $400. Where are you located at man? Good luck and have fun. Private gigs are a blast.