11950 Grand Commons Ave Fairfax, VA 22030 (map it) (571) 522‑6568 Watch your kids Climb the Pinnacle at the REI Fairfax! We went this weekend and it was fun to see how differently my two kids approached the wall. Both pretty much tackled it in character 
You can find details on hours (Wed 4–8, Sat 12–6, Sun 12–5) and cost (free for REI members and $5/ non-members) online, but ages are not mentioned. The belay staff on duty today suggested that the cutoff was about 30 pounds and/or ability to fit into one of their harnesses safely, but that little folks are not allowed to climb higher than the staff can reach. This rule was not an issue for either of my inexperienced preschool-aged climbers who were done with the wall before they reached that point, but proud that they tried. You only get one climb, and there may be a wait so this is just a short outing. There’s lots of fun stuff to buy at REI though.… (If you have any reservations about shared smelly climbing shoes you should bring socks. I think the smallest size they carry is 11.)
Update 10/2010: REI is still full of cool stuff to buy, but the climbing wall is gone. If your kids want to climb you can try Claude Moore Rec Center or Sportrock, both in Sterling. Make sure to ask about minimum ages (6yo at both places last I checked)!
