Khakis and a polo would be just fine. Make sure he has plenty of warm clothing. We got snow here today so be prepared if you're visiting in the next few months.
As for passes, there are four days for Thanksgiving, two weeks for Christmas, and a week for Spring Leave. Each semester, plebes are given one "base pass" which means they can leave anywhere over night for the weekend. A lot of people will take this pass on a long weekend (Labor Day, Columbus Day, Veteran's Day). It's also possible for plebes to get one performance pass each semester. Basically, if you excel in something you are able to put in a memo saying why you should be awarded a pass for something. For instance, my Beast company won best company first detail so I could get a performance pass for that. Plebes also get one religious pass each semester which can be used to go on a retreat with one of the various religious organizations, as well as a spirit pass, which means they sign up to attend an Army sports game not at West Point and get the rest of the weekend to do whatever they want. There are also tons of opportunities to get out of West Point with various clubs and other activities. I have not and probably will not use all of my passes this semester. I'm from the west coast so getting home and back just over a three day weekend is expensive, but I know plenty of people who've done it. There are plenty ways to occupy your time at West Point on the weekends, and if nothing else, it's always nice to catch up on sleep and homework! Bottom line, it is very possible to get out of West Point on the weekends, even as a plebe!
