Dr. Greg -
While I haven't been to all of the CW battlefields, I've been to a few. Gettysburg is the most powerful, mainly because it is so well marked, with so many monuments, and the has been the subject of so many books and movies. Last time I was there was with my son's Scout troop and we hiked everywhere. Great way to see the battlefield, although is was really, really hot and we all ran out of water.
Don't skip Antietam. It is close and interesting. Harper's Ferry is worth a stop too.
Enjoying the RR.