A friend sent me this link to a thread on dads riding motorcycles with their daughters. All ages, very cube-friendly.... and if you're a dad (or remember times with your dad), it could be a bit sappy... but still fun. And some great pictures, too.

Bungleau that was a great link for me :D

Though I do not aim at letting my kids ride till they are about 12.

Instead of picking an arbitrary age, just wait till they're big enough to sit on the bike with their feet comfortably on the pegs.

A friend of mine sometimes takes his daughter to school on his bike. He says that definitely scores a couple of points on the "cool dad" scale with her friends...