One way I like to share the hobby with the kids is by letting them help me out on my scratch builds. Although there are some things that they have yet to get there hands on.. Like flying my quadcopter, I always let them get there hands dirty and help me build. One great way is with painting. I give them their choice of colors and let them have at it. Red, and blue acrylic paint, plus a little mixing for purple.
Keep extra newspapper around.
They love it until the next day they come home to find that on the first painted flight.. You got a little carried away and use the plane as a lawn dart.. Now there are two parts to this plane.
So keep extra foam board on hand, and keep them busy.