Hello, Catherine,
Card trading at Walt Disney World "sort of" exists, but not quite like pin trading. I'd say it is more like card collecting. At the Magic Kingdom, guests can play
Sorcerer's of the Magic Kingdom which is an interactive game throughout the park where they will work to try and stop Disney villains. Along the way, they will be using cards to do different things and, thus, collect them. You can read more about the game at the
Disney Parks Blog, and there have been some updates since this article came out. You can also begin playing with cards beforehand, too, if you'd like as they are available online at the
Disney Store. And if your son is really curious, information about all of the cards is available at allears.net - just do a search for Sorcerer's of the Magic Kingdom Cards.
Thank you for your question. If you have any more, please don't hesitate to let us know. -Kara