I attend a school very similar to several of the schools you have listed (D3). From my experience, my overnight visits is visiting the campus for 24 hours. So, arrive in the early afternoon, go to a class with a member of the team, watch the team practice, go to dinner with the team at the dining hall, then maybe go to an on campus event (think lecture or fun crafty event, not-alcohol related) or to the library to study and then head back to your host's dorm room (you sleep on the floor in a sleeping bag or inflatable mattress, get breakfast at the dining hall, attend another class, lunch at the dining hall and a final talk with the coach before leaving campus. So, you're responsible for travel to and from campus, but the athletic department gives passes to athletics for recruits to eat in the dining hall for meals on campus from my experience.
It sounds like for your August unofficial visit, you'll talk to the coach, they might give you a tour of campus, and if anyone on the team happens to be on campus you might talk to them. It all depends if their pre-season or classes have started yet.
My school (D3) is known for its good financial aid, so anyone, regardless if they are a student-athlete or not, can receive need- based financial aid, no merit aid is offered. With your list of D3 schools being on the expensive side, financial aid will surely be helpful so college can be affordable for you and your family. It's just submitting your FAFSA and the other necessary documents. If you visit the campuses of the D3 schools, make sure to talk to the financial aid office, and if your parent brings you to the campus, it will be valuable for them to talk to the financial aid office as well. You could also give them a call or send an email. While the coach cannot influence how much financial aid you receive, they most likely have experience with the financial aid office.
Before you make your final decision, make sure to visit campus when the team members are there, then you can get a real feel for what being a student-athlete at that school is like and understand what the coach is really like and what they expect of you. And make sure you get along with the team members! You will be spending a lot of time with them, and you want to make sure they are people you want to be around!