65mph - if that is accurate - is amazing for an 8 year old. That kind of force can really put some wear and tear on his soft growth plates. My opinion would be to limit how much he pitches. Encourage your son to play catch and throw the ball frequently but limit his pitching. There is a difference between throwing and pitching. Definitely adhear to recommended pitch count limits as well as recommended rest between pitching performances. Also, as already mentioned, stay away from breaking pitches.
You can find pitch count recommendations on the here
http://www.asmi.org/]American Sports Medicine Institute (ASMI) website
. The recommendations are located [url=http://www.asmi.org/asmiweb/youthpitchcounts.htm[/url].
One other thing to be aware of is that the kids with the best arms tend to be the workhorses for their teams. This might seem great but it can result in those kids getting overused to the point they're physically and/or mentally burned out by the time they're 13 or 14. They may even be permanently damaged as well. So you need to watch this.
Finally, learn as much as you can about proper pitching mechanics, pitch types and recommended ages, and overuse injuries and how to avoid them. You are your son's best protection while he is young.