My kids needed a fairy story to get interested in Stonehenge. For my son, I told him a legend that the burial mounds were underground fairy houses, and the Stonehenge formations made "windows into a magic world," so as we walked around we looked through each magic window trying to spy magical creatures. When you visit, be prepared for WIND! It wasn't that cold when we visited, but overcast and windy. The kids did great (2yo in baby carrier on daddy's back, 5yo jumping to pose for silly pictures and looking for magical creatures) but we rushed around the circle once we got some good family photos, and didn't linger gazing at the rocks for very long, due to the chill. If you want to walk AMONG the stones (as opposed to around) you'll need to do a sunrise or sunset tour. If you're staying in London, that requires either a ridiculously early morning, or ridiculously late night for the kids.