how many do I plan for?...300?---500?

We Have a little vending gig at a very popular restaurant's weekly bike night. A normal turn out is 500-700 bikes. This week its a special Bikes, Blues and Barbecue. Live band and us vending our big old Pulled pork sammies. We are the only vendor! I'm thinking 300 sammies, but what the hell would I know....we are green as they come at this type of event. Now I know bikers love all three attractions, plus I forgot to mention the bikini contest....forgot to tell the old lady that part too...haha.
What do you guys figure? We make a full 1/3 pound sammie with a Pittsburgh style slaw. the sandwich is always a knockout at 6 bucks a pop.

Thanks fer the input in advance everyone!:-D

the complex is Quaker Steak and lube in sharon PA. It has a huge parking lot and mini amphitheater in the rear, vast majority will be in the parking lot the whole time. This is a very busy, popular joint known all around this part of the country. they have a beer tent set up every week on bike night. the bikes start showing at 5 or 6 pm till after midnight....band I imagine at 8 or so

http://www.thelube.com/sharon_PA/