V.W.
How into it is your family? For my son earning his 2nd Degree Black Belt in February (he's 13) we bought him a penny board. It was all he had been talking about for weeks. And it does seem pretty cool.
He also has a rip-stik, and my 10 yr old daughter wants one of those really badly. She has a cheap run of the mill wal-mart skateboard (and he has one of those too) but she reeeeeallllly wants a rip-stik.
ETA: They love the rip-stik. They DO need to read the instructions on how to use it though, b/c it is different than a regular skateboard. They sell a "ripSTER" and a "rip STIK". The RipSTER is shorter. The RipSTIK is longer. A friend of my kids got a ripster (after riding my son's ripstik) and seems to like it alot. She just turned 14. My daughter is 10, and she wants the ripSTER having used both her brother's and her friend's. The RipSTER runs about $79. The penny board was around $100-125, if I remember right. But you can choose any color combination, and there are tons. Son's is bright yellow with neon green wheels.
Just asked the kiddos, and they say you CAN use the ripstik at the skateparks and my daughter chimed in that it was more fun than a skateboard.