I just gave my DS his pin lanyard from our last visit (when he was 2), with his first official pin on it. He's been marching around the house with it on ever since I gave it to him! I think he'll catch on once he gets into the swing of things down there.
My DD, DW, and I do like pin trading, but aren't as fanatical about it as some people are. For example, I had one KID (couldn't have been more than 10) who kept looking at my pins, and telling me how much they were worth, and how rare some of them were.
What he failed to realize is that I don't trade pins for their value like that. My pins' value lies in being a remembrance of a previous trip, or other identifiers to me, or my family. My "Incredibles" pin represents my family (the movie hits home with me to an extent, with my family as well). My Magic Kingdom Fire Dept pin...well, you can guess there. My Monsters Inc pin represents our 2001 trip, when we saw it at WDW. My U.S. Flag Mickey head pin represents my pride in my country. My Milo Thatch pin represents my favorite of the underdog Disney movies: Atlantis. etc etc etc.....
But I digress......No. No guest has to trade if they don't want to.