I think your son should try in introduce himself to any coaches of colleges that he contacted before the event. Not all coaches will see everybody. As long as they are not on the field coaching a game I think it is ok to speak with them. Also he should thank the any of the coaches who are coaching his games. They may have some valuable feedback they would share.
The one thing as far as "stats" go was that several coaches looked on their sheets they have on all the attendees and checked GPA and test scores.
My one other piece of advice would be that your son is the who talks to the coach. I only spoke with one coach when we were at Headfirst last year. That was only because my son and I were walking to the car together and he stopped us. I thought it was not place to speak with coaches. But that was just me.