To me, Manassas Battlefield was like stepping on hallowed ground. On the day we visited it was a misty, May morning. We arrived early and there were only a few visitors. As we stepped onto the battlefield and saw the long line of cannons arranged as they were during the fateful battles, it was easy to imagine what it must have been like.
For historical buffs, Manassas (or the Battle of Bull Run) is a must. It's about $3 per person, and another $3 to see the movie there. The park service has done a great job with the museum. There are plenty of artifacts, and there are a couple of scale models that are animated with sound, so that you can truly understand what happened during Manassas I and Manassas II.
When you arrive, check at the counter with the park staff for a schedule of tours. We went on a couple of different tours the day we were there, and it really brought the whole experience to life for us. While waiting for the tours to start, meander through the museum exhibits.
In my opinion, this is a great stop for families and anyone interested in Civil War history.