For anyone interested in playing percussion(drums) an electric drum set is not for learning. It really is more like a toy. That said, it may be exactly what your son likes.
My DS14 plays drums at school band and in a garage band(with gigs & all). He has never had any formal lessons except at school, which really does not count for actual instruction, but I digress.
While he has a full drum set, and wishing it were better.......he'd have fun with the electronic set but the fun would wear off.
So, to sum it up, you have to decide how they are going to be used.