I would listen to your son's advisor.
Before the combine when keewartson was drafted, he was invited to a "workout" at XXMLB team. I almost had the flights booked, when keewartson said his advisor recommended not to go. I couldn't understand.
His reasoning: If he went, he would have to go to all of them, or it could show some sort of favoritism toward the the team (and we couldn't have that, now, could we?! ) He had already turned down another team's invite to a workout. Maybe the combine avoids this.
Will all the teams be there? Did he play at a school (or against schools) with lots of exposure? Is "meeting with a lot of scouts" 7 or 30 teams?
I never talked to son's advisor before the draft. But I would have your son get an explanation to why he suggests not to go.