Jester Park is a hugely popular park, with lots of options. The natural playscape sits alongside a bison and elk herd, several campgrounds flank miles of wooded trails. Discovery Pond is a beautiful spot to explore, and there is regular nature programming held throughout the park. They are currently building an indoor nature center in the middle of the park, but the detour signs are clearly marked in order to acces both sides of the park. There is easy creek splashing access here, you can see more specific details about how to get into the water in this post.
Chichaqua Bottoms Greenbelt is lush and green, with a winding river next to the grass trails. Several wild bird species are on display towards the park entrance, and a historic bridge is fun to look at.
Walnut Woods Park is a short drive from anywhere in the metro, but feels like you’re out in the woods. There are trails as well as a traditional playground, along with a busy bird blind. The playground is small, but has rubber footing under the playset and swings (there is a sand pit, however).