Hello Tracie! Your question makes me so happy, my family loves pin trading at Walt Disney World and I just know your kids will love it too!
I wouldn't worry too much about scrapper pins. Although, I am sure it happens, I have never seen a Cast Member turn a child down for a pin. Per the
Disney Parks Merchandise website, the main criteria for a trade-able pin is that it must be a metal pin with the copyright symbol next to the word "Disney" on the back. The pin should also be in good condition with no damages. For safety reasons, you are also asked to trade one pin at a time, hand to hand, with the rubber back on. Something my daughter likes to do is look for the Cast Members that have the green lanyards with pins on them. Those Cast Members only trade with children, which is fun and makes kids feel special. When my daughter first started pin trading, I had her think of a common theme she wanted to collect. Some ideas I suggested were a certain character, a specific movie, a color she really liked, just something to give her some direction. It worked like a charm and we spent our vacation building her collection with pins she really enjoyed.
In the link above, you will find other guidelines and tips for pin trading. It is really fun and a great way for the whole family to interact with Cast Members and make memories that will last a lifetime. I hope this helped, if you have any other questions please come back and ask.
Happy trading!