You could visit W&M and Richmond on the same relatively short trip. And you could visit Wes and Brandeis on another trip. (so, two total trips to visit these schools).
Or you could take a week or so and visit them all. You could fly into Boston and start at Brandeis, then head to Wes, then head down to Virginia for W&M and then Richmond. You could fly home from D.C. (or start in DC and fly home from Boston…)