All of the above advice is absolutely right.
Our son attended the Richmond camp three years ago. It was great. He ended up at a college that recruited him from there.
They won't list coaches as attending unless they are - so, barring emergency, listed coaches actually show up.
Coaches really looked at each players. They did not seem to come with a pre-established list of players to look at and ignore the rest.
The first questions coaches asked was "What is your GPA and SAT/ACT?"
If your player is interested in a particular school, he might want to e-mail the coach before to let him know that he was looking forward to introducing himself at the event.
I did not see too many coaches chase after players, but players did line up to talk with coaches.
Let your player approach the coach and do the talking, unless the coach asks to talk with you.
On the car ride there, I practiced with our son how he would approach a coach. It gave him some confidence. After the first discussion with a coach, it became a lot easier.
Keep it fun.
Best wishes.