The great thing about geocachers in our neck of the woods, is that they're really eager to help others, especially kids. I would consider attending an event and let people know that you'll be bringing kids that want to learn. Or better yet, host a Geocaching 101 event specifically to show kids how its done. In either case, I bet you'll get lots of cachers willing to let the kids borrow their GPSr's for a few hours as well as learn tips from the pros. You can also advertise that your scout troop is looking to purchase used GPSr's at a discounted rate, or maybe take donations from cachers who are no longer using their older units. A container making table would also work for both kids and adults alike. Oh, and CITO's make great scouting service projects.
On the Waymarking side, you can easily get away with visiting waymarks without a GPS though online mapping tools like Google Earth. You could show them alternative methods of mapping and aerial photography to find things. I can only imagine the badge earning potential through geocaching and waymarking.
And don't forget the appropriate scouting categories that the kids could set up waymarks - scouting headquarters, eagle scout locations, camping spots, etc.
Also, a lot of our geocaching friends are scout leaders so there are probably resources right under your nose!