bballmomssr,
It's kinda like fishing, you never know when they are bitin', and there are a few times that fishin' ain't allowed.
But, when they the coaches fish, catchers are often, what they are trying to catch.
The coaching fraternity is a pretty tight knit group.
So, your son might be seen by another coach visiting the camp, or the host coach might see a player that he thinks can help another coach out and make a call.
Go to the camp, hustle, and tell the coach he is looking for place to play.