Some good advice on this thread.
I would agree that many of the camps are fundraisers. Some colleges recruit from their camps, and there are folks on this board who can report success from attending a camp. In particular, my impression is that some D3s rely heavily on their camps since they don't cover as much territory recruiting-wise.
If a coach is already seriously interested in your son at this time, you will know it. However, that doesn't mean he can't get some interest at the camps. I would certainly suggest direct contact with the coaches, with an explanation of the circumstances. It really depends on where they are in the recruiting process for your son's position.
I should add that my son got a call from a HC based on word-of-mouth of a very trusted source. He got an invitation to the college's camp, did well, and will be attending there next year with a guaranteed roster spot. However, it was VERY clear before he attended the camp that the coach was serious about recruiting him based on the information from the trusted source(s), but wanted to see him in person.
Good luck!