I'm preparing to take a horse off to college with me, too. =)
To me it seems like your best bet would be to board him at a stable where he will be taken well care of, unless your parents/sister are okay with taking care of him at home. If they are, then go for it. Bringing him home from the barn during the summer break wouldn't be a big deal, since it's a couple months, but I don't see a need in bringing him home for the shorter breaks such as Thanksgiving and Christmas. If your school is only thirty minutes away, you can easily go see him during the breaks, and there won't be a need to interrupt his routine. Most horses deal with change surprisingly well, so I doubt bringing him home during the summer would be a big deal for him at all.
You just want to be sure to put him in the place that is best for his well-being. With you being in college and being very busy, the stable would insure he's always taken care of.
every ride counts.