PP. here is the info https://lakesidebrooklyn.com/visitor-info/splash-pad/

There is a very nice splash pad with sprinklers in Prospect Park where the skating rink is in the winter - LeFrak center at the lakeside. It's closer to the Southeastern corner of the park. It is not too far from the Brooklyn museum, probably about 20 mins walk for an adult, but given the heat, you'll probably be best with Uber.

Warning for the adults: wear something that you wouldn't mind getting splashed because you will get a bit wet there. And wear water sandals.

And we call them sprinklers.

You'd have to Uber over but this place is great and the whole park is a wonderful place to hang out: https://www.brooklynbridgepark.org/places-to-see/playgrounds/water-lab-at-pier-6/

Visiting Manhattan with my MIL and kids. My MIL really wants to go to the Brooklyn museum and possibly the botanic gardens tomorrow. It’s going to be ungodly hot and I was hoping to pack bathing suits and take my kids somewhere they could cool down a bit. I’m seeing some in Park Slope and Prospect Park but it’s hard for me to get a sense of how walkable they are from the Brooklyn museum (for kids who have been walking all over all week and will be tired and hot). Advice? It looks like maybe Mt Prospect Park is attached to the Botanic Gardens but I don’t see a splash pad there. Used to spend time in Brooklyn and NYC pre-kids but it’s been awhile.