My 2016 went to one D3 prospect camp the fall of Jr year and then none last summer/fall. We were planning on several last fall and then around this time, post HF on LI, he started getting requests to come visit. If the showcase you are referring to on the east coast was HF then you still may hear from some schools - the last week of Aug was when the majority of his "official" interest started coming in.
As I noted in another post a minute ago - none of the schools that were interested in him asked him to come to their camp. I will say that HC at the school he's attending did tell us that there were several players attending the camp (last year) that they were looking at but they made it seem like those players knew it and it was just a matter of the coaches seeing them live - there was discussion about it before hand. I would not attend a D3 camp at this stage without having your 2017 try to discuss with the coach before attending. As noted by some others - honestly tell them that he's visited the school already, they are high on his list and he'd like to attend the camp but he'd like to know if he's under consideration and where he falls on their list.
We have good friends whose son attended our son's school's prospect camp the Sunday after we did our visit on Fri/Sat. We talked to the coach at length on Fri when we sat down with him. He told us that they needed 12-13 players and 5 pitchers - and that they wanted our 2016 to be one of those pitchers. He also told us that the only position they really didn't need was catcher. Our friend's son is a catcher (who later committed to another great D3 school) - he had a great camp and after they told him they liked him but that they already had their catchers set for that year. So it was essentially a wasted trip for them. At this point with what you've spent already and with the time you have left you'll need to focus on where there may be a real opportunity (I know, easier said than done sometimes).