My suggestion would be to do the old black and white, maybe drive in theatre, look.  You could run red carpets along the front of your tents, have a little cd player playing the old time music from the movies that were just sound and park some older cars from a car show out in front of a big projection screen where you could have a movie like Casablanca playing.  For the "snack bar" have your first tent set up with some green tea, cranberry juice, apple juice, and drinks like that, your next tent with no salt/no butter popcorn but with the seasoning provided on the table and some "I Can't Believe it's Not Butter" spray in a can of ice, serve it in little brown paper bags.  The next tent could serve some all turkey hot dogs with no or low fat toppings, the next serving no salt nachos with salsa instead of cheese, and so on.  Blow up clip art of old time movie reels and images and post them around the campsite.  Also get the teams to create their own movie posters that could be displayed at their tents or around the site.  See if you can borrow some line dividers, you know the metal poles with the ropes, from a movie theatre near you and set them up.  When teams sell items, have them give tickets (to look like movie tickets) to the buyer and have a raffle at the end of the night, displaying the winner's name up on the big screen like credits.  Anyway, just some ideas.  Hope they help.  Good luck and I really like the idea.  I don't know where you are located, but your best place for your event sounds like a drive in theatre.