The most important thing is that he is willing to hit against the wall for hour after hour. Make sure the coach really knows technique well and teaches it to him correctly. If he has good fundamentals and is willing to practice it over and over again hitting against the wall (including the serve) that is really the basics of what you need at this point. Of course, you do not want to ingrain bad fundamentals so the coaching is important. Other than that, just let him keep progressing, playing against better and better opponents as he improves and see where he is in a couple years.
If, at that point, he is still consumed with tennis, competing well against much older kids, and is getting too good for anyone at the local area, you might think about bigger things. Right now, let him still be a kid playing tennis instead of a tennis player who is a kid.