I second Nuke's advice. If you are targeting D2, D3, his current and projected skill set (and size) on the mound will likely get him attention. He should focus on continued efforts to maximize that skill set, get the best grades he can, start narrowing the school search and figure out the best way to get in front of those schools. If it happens to be another PG Event, then you can kill 2 birds.
Does he play with the right travel team that will get him in front of some of his schools next summer/fall? If he is at the right events, there will be guns out.
To answer another question you had.. If he knows he wants to be a P in college and that is the part of his game that stands out, then yes, I would attend the next PG event as a PO. We can't see and don't know your son so this is a very general suggestion.