You could always set up something like we have at our store. I donate a ton of commons and uncommons because I typically buy a playset of those when a new set comes out so anything I get after that is extra. We put them in this little machine you put in a quarter and get some random assortment of cards out of.

Since it's not worth it to get only commons and uncommons, the store owner puts in stuff like actual duals and some other goodies every so often. That stupid machine is a hit and spreads the good cards among the kids since most experienced players steer clear of that thing. I've seen people use grab bags in a similar fashion.

If you want the kids to get in, you should ask the store owner to try it. It's amazing how much money that little thing makes. It's hard to get the good stuff, but it does happen and it's almost always a kid who gets it. Now if we can just keep the assholes from trading the good stuff off those kids for nothing.