I went to the first one after Disney started having these in the Contemporary's Convention Center. That one was so mobbed Disney opened up another room. I like the space better than when it used to be held in the Contemporary Lobby.
I've been to a couple more since. Disney does have an official presence at these things, lots of CMs around. They also have had a kids-only area, where kids (not sure of the ages) can go in and get trades off a trading board. One time I was able to buy LE pins that were *only* available at the Pin Night.
Yeah, there are sharks there (sharkiness is kept to somewhat of a minimum, since everyone is on Disney property), but there are also some really nice people and most of the real collectors get a kick out of little kids trading. When I go to WDW, I usually have some pins that I make a point of just giving away, mostly to little kids.
I always have a blast at the Pin Trading Nights. Just be prepared for a crowd and be prepared for some of the guests to be really picky. It might be overwhelming to little ones. And all those pins on all those tables....kind of dazzling, even to adults :

.
YOu might want to check out the trading boards at most resort gift shops, plus some resorts (Port Orleans is one) brings out a trading board in the lobby at certain times. Anyone can participate, not just WDW resort guests.
agnes!