There use to be some candy called Pop Rocks. (and there probably still is, but I haven't seen it in a long time) They were like sweet little crystals and when you put them in your moth they popped all over inside your mouth. I can't say they were my favorite candy, but I did have to try them a time or two. I wonder if that is what is in the ice cream and chocolates.

It sounds like you made a very fun game out of your coin cookie snacks. Education and fun snacks all rolled into one.