E-skating is no more dangerous than classic skateboarding. On the other hand, some models will allow you to go quite fast, which can be dangerous for children. According to my own experience, a child can start skateboarding around the age of 5-6 years old. As far as driving an electric skateboard is concerned, it is not the same thing, the difficulty is to trust it by giving it access to a motorized vehicle. I would rather advise to wait the 10-11 years old for an electric skateboard. The best thing to do, in my opinion, is to make your child aware of driving a normal skateboard, then to buy him an electric skateboard, if he likes it (other vehicles exist if the skateboard does not suit him).