Parks have people. This park has people. Not only New Yorkers, but Brooklynites. They don't want to be messed with, but they're often happy if invited to play. There are ways to engage them, use them as sets and game pieces. They have agency and autonomy, just as you do, and they want to play and have a say in the rules they play by, just as you do. They can actually be a really really fun element. I'll think of more ways to use them and you can too, but don't be afraid of them.

As an example, one gameday, I had a three absurdly large balloons. I had a small errand to run in the forest (putting up my I Ching hexagram, not peeing, sheesh), and my friend stayed behind to guard the balloons. One was missing when I got back, replaced by a boy asking for one of the other two balloons, explaining that he had seen someone else with a balloon and heard about a balloon game. My friend explained the rules (which he had earlier explained to another child, from whom our current young one had seen and heard explain the game.) "We can give you this balloon, but it can't leave the park, so when you leave the park, you have to give it to someone else."  

Now we were down to one balloon, which was shortly thereafter adopted by a grandmother and her two young children who had themselves just seen a balloon and heard about a game, and they wanted to play. I don't know where the balloons ended up.