Great advice by others. I would add.. yes, a track coach can work on speed and running form but it would also benefit to include agility as part of the focus (most track coaches can accommodate - just be sure to bring it up). A big guy doesn't have to be straight-line fast but is much more attractive and effective if he can maximize his athleticism and move fairly well. This can also help a young athlete navigate the awkward growth stages with a bit more grace, among other performance benefits.
I think we are all assuming he is getting good pitching instruction. If he is attending those team events with that size and those numbers now, I'm guessing you will know when it's time to start pushing the contact buttons and hitting the PG events. PG will rightfully argue that there can certainly be benefits to early participation. Smart spending is a factor for most.