Count me as another vote for Nerdkits. I -so- wish that I had gotten mine when I was a teenager. But even having just gotten started as an old codger in my 30s, I'm amazed at how much I've learned from the amazing kit and instructional videos that the Nerdkits team has put together.
Trust me--if you have a child who is old enough to use the computer by themselves and shows the least interest in programming, inventing, or even just has a tendency to take apart their toys (whether or not they're able to successfully get them back together again), get them a Nerdkit and help them assemble their first few projects. I think you'll be surprised at not only how much you both learn, but at how much fun you'll have as well.