Thanks so much for everyone's thoughtful suggestions!
We're leaving in FOUR DAYS.

I bought a pair of Hoka Bondis and a pair of Topo sneakers. I'm going to alternate those at the parks. I also want to bring sandals to the parks in case we get caught in the rain- I tried two different pairs of Tevas, but they just weren't comfortable. Something about the straps was wrong. I got a pair of cushy flip-flops from Born on clearance. I know most people say flips are a no-no, but I live in them over the summer so I'm thinking that as an emergency back-up for soaked feet they'll probably be ok.
Honestly, I'm worried about my choice of sandals. We'll see! I'll report back!