First, look presentable. Just because your camp is located in a wooded area in the mountains doesn't mean you have to look like you have been living without the amenities of modern life. Take a shower, get a haircut, iron your shirt, press your pants, and brush your teeth! It's fine to wear your camp's logo attire, but make sure it is clean and fresh.
Second, get out from behind the table! Stand in front of your table and SMILE! You need to greet people as they come by; a simple "hello" with a bright smile will work wonders. So many times we see camp directors or representatives of the camps who sit behind the table reading a book or eating lunch. These people then probably proclaim that the camp fair was not very successful. Bring two representatives with you to help the day of the fair, that way everyone gets a lunch break in the director's lounge.
Third, don't overwhelm the parents. Speak in a soft tone. The parents are checking you out as a possible role-model for their child. You want to make a connection but you don't want to come on too strong. Many camp directors will have little giveaways on their table for the kids to help them remember the camp director with whom they spoke.