It costs nothing to play the game the only requirements are that you are a camper that has paid to camp, you have to be 18 years of age or older and you can only play 2 cards at a time. The winnings are "wooden nickels" that can only be spent at the campground.
Native American Law Attorney
Yes the activity is probably legal since there is no consideration. But this depends on the value of the awards and the rules governing the game.
This is not intended as legal advice. It is only provided for educational purposes and cannot be relied upon as legal advice. Further no attorney client relationship is or has been formed by answering this question.