I was remincising about the Smokies in your previous post, so beautiful, so haunting.
It's been 20 years or more since we visited the Smokies. On our list "soon," as you measure "soon" when you have a baby every two years :-). You have to plan outdoors-type trips so the "previous" baby is walking, while the "current" baby isn't crawling yet!
There are lots of smaller sites in Virginia. My father, brother, and I visited the "Saylor's Creek" site, one of the last engagements before Appomattox. The terrain is very 19th century; you can really see what it was like for the soldiers.
My husband and I missed the Manassas battlefield (which Mom and Dad say isn't that great), but the City of Manassas Museum is terrific. We spent a whole rainy afternoon there, touring the place with an equally-lost couple from Alabama. (Thank goodness it wasn't Yankees!)
For Gettysburg - which we saw in early January, with a toddler along - I recommend getting the Army War College Battlefield Guide. That was such a useful resource. The dead are awfully thick at Gettysburg, though. One of my friends, who's not usually sensitive, said she couldn't get out of the car when she was there.