I've been running a Robotics Club in my local elementary school for 2.5 years now. We have a Mindstorms NXT set and the club is always very popular. One thing that helps is having interested parents. Several of them wish they had such a club as a kid so enjoy helping! One of them brings an NXT set from home so we have two to use. I show videos of robot-related things (funny commercials, industrial robots, trade show robots, Robo Wars). I also manage a junior high team for FLL and challenge the K-6 kids with similar challenges. Some of them love to build, some design, some program, and of course I encourage them to take turns. I have about 1/3rd girls, the rest boys. It's a lot of fun!
Feel free to contact me for more details.
http://www.ariankulp.com/