When we were at the arboretum, Katherine found her friend Henry from school. Henry's mom was there selling soap and he was facing a long day just hanging around, so he was very excited to see Katherine!
Since we were in a safe, laid-back place I let Kate run off on her own with Henry. She relished the freedom to roam in a public place. I checked in occasionally to see what she was doing. I usually found Katherine and Henry at the big swing.
At first I was concerned that they might be dominating the swing and not letting other kids have a turn. But then I realized that they were basically running the swing event. They pushed each other when no one else was around, but they hopped off and helped any little kid that wandered near. Twice I even saw them talk women in their 60's into taking a turn! They were quietly and responsibly supervising the swing and having a great time doing it.
When I drug Kate off to take some photos of her, Henry followed. After the pictures, I watched them climb a tree and then showed them how to make "snow" under the spirea hedge (a favorite game from my childhood).
I'm pretty sure Henry and Katherine could have played happily all day long. It was such a beautiful setting for a couple of good friends to hang out, just being kids.