I would start calling and emailing these colleges asap to make these visits as productive as possible. Some of these schools like Barnard and Haverford strongly encourage on-campus interviews. I would schedule those interviews.
I would schedule tours and info sessions asap. Some fill up fast. especially on Saturdays.
I would also reach out to the Philosophy Department heads (or other depts you’re interested in) and try to schedule meetings You’ll learn a lot about the department, and it will better inform your applications. My D had one dept head from a selective college contact admissions on her behalf just based on a meeting.
I would also try to schedule sit-ins on classes which interest you. Also, I would research what student activities are going on and attend - sports, improv., theater etc…You can learn lot meeting and observing current students.
With my own kids, we did a lot of groundwork prior to all visits, which I think really informed their decisions and applications One of my kids is at Haverford and one is at Brown, and they visited several of the other schools on your list. We actually passed on visiting some schools that were not accommodating
Keep a journal during your visits - It will greatly inform your applications.
You could cluster visits as follows:
Wellesly and Brown
Yale and Weslyan
Williams is stunning, but way out of the way. We combined it with Amherst and Smith.
Columbia/Barnard
Princeton
Swathmore/Haverford/Bryn Mawr