Comment by kurthr

Once you're selling them, put a bounty where kids can turn in the cards for money. Then you'll both set a price floor and know which stores are selling them and you can find out who's doing it. Nothing says that a token has to last for a constant amount of time. If kids turn in more than a certain percentage, then that location would have theirs expire early.

What I like here is that you've turned a digital problem into a physical one where we already have solutions and intuition for how to enforce rules.