Visits are an important part of the search process. If your son has some ideas or interest in specific schools, and you can work it into a vacation or days off, it is helpful to get out there and take a look.
The earlier you start college visits, the less pressure there will be come fall and the more fun it will be. If you wait until senior year you will both feel the stress of trying to fit them in. If you are visiting, try to schedule it so you can have an official tour because this is where you will see facilities, a dorm room and hear about specific programs.
Although everyone tends to have a lighter schedule in the summer, I strongly advise you and your son to go on some college visits this spring. Colleges will close for the summer around mid-May, so there won’t be any students on campus. It is very difficult to get a gauge for student/campus life when the campus is completely quiet. Visiting while college is still in session will provide your son a more accurate view of what the environment is like on that particular campus. Due to the pandemic, please verify with the college that they are offering in-person visits before you go!