Designing your own switch plate is pretty craftastic. Some of our teens got really into it and made a lot of layers. Thankfully, switch plates are inexpensive, which means people can make more than one. The clear chalkboard paint may be a little pricey, but you can always do the program again. I would recommend painting the switch plate covers with chalkboard paint before the teens arrive. Then, you may want to remove the screws, as some people like to glob their paint on and might make the screw permanently part of the switch plate. Also, hairdryers and tweezers come in handy. You may want to consider glow-in-the-dark adding paint to make an even more interesting program. Have fun!
This link has the directions we followed and many other good ideas: