If your son plays summer and fall travel ball (like my kid), then I assume that there are only a couple of open weekends. This fall was pretty typical: two weekends with no tournament scheduled in September and October (reduced to one weekend after a rainout and a make-up event). It turned out there were no camps of interest on that one weekend.
I don't think son's coach would get bent out of shape if he skipped a typical weekend tournament to go to a camp at a school that was actively recruiting him, but I don't think son would want to do that more than once in a season. (I'm not aware of other players on the team doing it. Could be I just didn't know why they were gone on a particular weekend.) My son has gotten some notice from college coaches who saw him at tournaments. Otherwise his in-person contacts were at Headfirst--after the summer season had ended--and he may do a similar multi-school showcase after the fall season ends.
I've been involved in a few threads here on camps... but I still feel like I'm missing something, because I don't really get how camps could be a major element of recruiting. 
Timing, targeting and cost all seem to weigh against them. If XYZ University is recruiting your kid, is nearby and their camp happens to be on a weekend when your son hasn't already committed to play with his travel team--then sure, why not? But mostly the camp invites don't seem like useful recruiting tools to me.