DH lived in DC for 3 years, I used to see a friend there frequently when I lived in Philly, we have taken the kids twice. We have seen all the major mid-Atlantic cities and most of the ones on the west coast. What we haven't seen is the South so that's why I thought of the places on my list.
I am going to check out the Atlanta day trips list. I think I am leaning in that direction. Then I have to think of what place to stay and wonder if I can find a VRBO....hmmm