What region of the US are you in? I road race myself with the WKC on the east coast. The KT100 is a solid choice for a starter motor, since he’ll be 15 he you can put a SBX muffler on it and go. You should look for a sprint CIK kart, that will allow you to race at sprint tracks also. Of course, you’d want a sprint-enduro for the full road racing experience. But the speeds will be higher also.