The first camp I worked at had a visiting weekend between the two four week sessions for campers who were staying all eight weeks. To avoid problems of parents arriving ridiculously early, the camp set an arrival time (it was like 10 AM, IIRC), and until then the gate on the road to camp was closed and manned by a couple of staff. I was on duty for it one year and we kept seeing parents drive by like starting about an hour and a half early.....they knew better, but that didn't stop them from trying. :-)
The camp didn't run any formal visiting program really, in fact, most counselors had that weekend off. They did ask that some lifeguards stay so they could keep the waterfront open, but other than that the staff was off after lunch on that Friday, by which point the vast majority of parents had arrived. Parents generally spent some time at camp with the kids but almost always took them off campus for a large part of the weekend. For the campers who didn't have any visitors, some senior staff organized a few out-of-camp trips and such for them so they were kept occupied. Mostly though the camp let the parents know that if their kids were staying the full summer, the parents (or at least some relatives) were expected to come up on visiting weekend if at all possible.
Homesickness wasn't too huge of a problem after visiting weekend for two reasons. One, come Monday a whole batch of new campers arrived who were only staying for the second four and that kept the full-summer ones occupied. Two, most of the eight weekers were older returners or, in the case of young ones, they often had older siblings at camp. Those are the types of campers that were least prone to homesickness, in my experiences. That's not to say that we didn't have SOME homesickness after the fact, but by and large it wasn't anywhere near as serious as what we might see from totally new campers only arriving for the second four who might never have been at camp before.
