That fact that he is an experienced dirt rider AND responsible helps alot. But, as you probabably know, riding a road bike is very different. He won't have to worry about the mechanics like shifting, but will have to get used to the bigger weight, watching out for vehicles, etc.
MSF training would be great, he would have fun.
Also, maybe you can get him used to some routine safer routes (i.e. to work, or school) for a while before venturing out.
