As you know, the Jr-Sr summer is very important time in the recruiting calendar. Attending any is only helpful if you differentiate yourself for the others in attendance. From our experiences hope to get your max bang for your time and buck:
If you have an idea of what schools your son wants to attend, try to find out what showcases and tournaments most of them will be attending early in the summer. Make sure that they will be in attendance or if the showcase has a reputable and very good reporting system to these schools such as Perfect Game. If you can afford a couple it would be great, if it is Perfect Game, some showcases have more colleges in attendance than others.
I terms of tournaments, make sure that the team will be attending tournaments that will be scouted with coaches that your son in interested in attending or let the coaches that you are interested in know that your son will be attending the tournament and what the schedule is by way of inviting them to attend the tournament to watch your son, obviously you have already established a recruiting process with the school.
If you are getting genuine attention for a specific school, at that point I would attend a college camp, unless you want to use the camp as a way of validating if your son wants to attend the school and you want to check out the coaching staff. If you are looking only to get exposure to the school for recruiting purposes, I would not attend until you get the genuine interest from the coaching staff and they are going to be there, unless you are planning on putting on a show, either case, let the coaching staff know you are planning on attending their camp and you are interest in playing for their program.