As a father of three, I can say that the idea of any of them riding on the street scares me a good bit and terrifies my wife. My youngest is an avid dirt bike rider and the most likely to want to ride on the street when he is old enough (4 years from now). I'm not sure we will allow it until he has a lot of time behind the wheel. If my wife has anything to say about it, a bike will be out of the question and we will have to deal with the hypocrisy of my daily riding.
I think a few years of solid and responsible time in a car will help him learn the rules of the road as well as teach him to understand how things happen in the real world before we let him unaccompanied on 2 wheels.