Our son was also younger, 16 in the fall of his senior year. OV’s definitely helped him rule out 2 schools, and moved 2 up the list.
We did not attend the OV’s, but stayed until the coach came and then we left. We enjoyed the sights surrounding 2 of the schools and stayed in a hotel nearby. 2 others were within driving distance, so we did a drop off and pick up.
I remember at one (a drop off) the parents were shocked I wasn’t staying and hanging out. First, I live an hour an 45 mins. from the school…nope…heading home! Secondly, when I turned to look and say good-bye, he was already long gone… 
DS20 will be a young senior too (16-yo as well). He has traveled a lot, but never alone. I feel comfortable for him to go to the east coast school that is 4-5hr away all by himself, but am a bit queasy for the other one that is on the west coast, with no direct flights. That school’s coach has just emailed him that parents could join for a meeting with the coach on Friday. Even if I do go, I will be doing my sightseeing and let him have his fun, I guess.
D3 track parent here. My S went on 2 OVs. The first one was a recruiting weekend for several athletes; the coaches brought them to/from the airport and managed everything. I did not go. We had visited the school already on a private visit.
The second, I had not been to the school so I wanted to see it. I did fly with him but dropped him off on campus and stayed with a relative in the area. I did the admissions tour on my own, and before I left we both sat down with the coach.
Son also did all his OVs alone. They were all relatively long, cross country flights and it wasn’t practical for us to go with him. He learned a lot on these trips and it really helped him crystalize what he was looking for. He got a good feel for the team culture, as well as the school. He handled the entire recruiting process himself (although he did let me proof read some of his longer emails). It made me crazy nervous - I kept asking him to cast a wider net, but he knew what he wanted and in the end he got what had been his first choice. I am proud of him for managing this process solo. I think the coaches want the kids to be in the driver’s seat. I think that kids need to have a lot of confidence to get through this process successfully. We know other kids who had talent in his sport, who gave up trying to participate at the college level during this process. Anyway - good luck - I would say OVs are important and it is best to send them on their own. It was also nice as coaches picked son up at airports and got some extra one on one time with him during transit. I think that was good for both sides of the equation.
I went along to join the campus tour at the front end and meet with the coach over breakfast the next day, but she was in the hands of the D3 VB team in between for class, practice, hanging out and sleep.