I think this thread popped up b/c many people haven't been to a Convention, and they don't know what to expect. I wonder if some people have a "HIN" type of concept pictured in their minds.
Fridays are typically the track day, and food/tent could be a good thing on Friday (depending on what the track offers). Some tracks have concessions and/or places to sit in the shade. If this track does, then something else could be used. If it does not, then food/shade would be helpful. I wouldn't decide on a price until after you've calculated your costs - but cheap is always good.
Saturday = free day.
Sunday is the car show, and that will be catered (typically). So a tent/food shouldn't be needed that day.
Josh