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).
Island Park feels more like a campground, with a playground in the middle, I don’t think I’d go back just to play. The river running nearby has a metal bridge going over and you can see the dam.
Kuehn Conservation Area is a large park with very diverse plants and habitats, with extensive trails. At the front of the park there is a large tipi, which is used for the annual Prairie Awakening Celebration. It’s easy to feel like you’re in the middle of nowhere in this park, with lots to explore and a bird blind to check out.
Pammel Park has a lot to offer, with historic sights to see, extensive trails, a nature center, and the only highway tunnel in Iowa. Middle River runs through the park, with a ford providing perfect splashing for kids. There is easy creek splashing access here, you can see more specific details about how to get into the water in this post.