My girls, ages 9 and 11, love pin trading with CMs. We use these locking backs:
http://www.ebay.com/itm/322038013748?_trksid=p2057872.m2749.l2649&ssPageName=STRK:MEBIDX:IT
I don't want them to have scrapers so I buy the mystery bags so if they get duplicates, they trade those.
http://www.ebay.com/itm/252478314277?_trksid=p2055119.m1438.l2649&ssPageName=STRK:MEBIDX:IT
We have seen fakes on the Cm boards but my girls are old enough to avoid them now. And if you get something you don't end up liking, trade it again!
My girls got chosen to be honorary CM on officers pin trading night. It was so fun! They got a CM black lanyard loaded with pins, and they traded with kids and adults as if they were a CM. Of course they had to give their CM lanyards back at the end of the event, but they had a lot of fun!