At WDW, any metal pin with a Disney backstamp on it is tradeable, meaning it has "(copyright symbol)Disney" or "copyright Disney".
A couple of things...
Usually
Disneyland pins are highly coveted by WDW traders.
At first, your kids should probably only trade with CMs, be careful of letting them trade with other guests, some adults/"sharks" might try to take advantage of younger traders.
Check out
www.pinpics.com & dizpins.com. Those are two good fan-sites about Disney pintrading.
If you want to know if the pins you now have are rare/common/etc, go to PinPics. Put a general description in the pin-search engine. For instance, you might have a Disneyland Donald Duck pin wearing a swimsuit or some such. Put "Donald swim", check "Disneyland only" and whatever Disneyland pins that have Donald in a swim suit or swimming will come up. Then you can look at the pin info to figure out how many people want the pin, how many people have it to trade, etc. If you have a pin that 300 PinPics people want, but there is only one available for trade on PinPics...you have a *very* valuable pin.
I second the post that says to check out the Collectors' Board.
(Btw, I looooooove pin trading & collecting

.)
Happy trading

,
agnes!