B.C.
Luray is a great trip. I don't remember strollers in the caverns themselves (I remember lots of stairs).
Another great trip we did a few times was Cass, WV. It was about a 5 hr drive from northern Va one way (I think we spent 1 overnight at a ski lodge nearby, but in the summer the place is fairly empty).
We'd take a lunch and take the steam engine train ride up the mountain, have lunch at the top, then ride the train down again (they have a real nice switch back). My son LOVES the train!
http://www.cassrailroad.com
On our way back we stopped at the National Radio Astronomy Observatory at Green Bank, WV. The telescope is HUGE!
http://www.gb.nrao.edu
Harper's Ferry is a nice day trip, too.
Have fun!