For a player your son's size, that's very good.
He is primarily a 3rd Baseman, correct? He will probably get a little faster as well since he is so young. EG over at Vanguard. Didn't think I forgot did ya' ? How is he doing?
A position player doesn't necessarily have to be fast but it helps in most positions other than corners and catching
It could help there too at times. HSSBW has a section on main page on scouting which display scale used by Major League Scouting Bureau that will be helpful. Hope all is well over your way.
Best Wishes,
Shep