The ford at Pammel State Park in Madison County is such a fun place for kids to splash and play. There's a sandy area, so I recommend bringing some beach toys. Nets are also great to have.
There are a few covered picnic tables near the ford, but no restrooms. The closest restrooms are a 1/2 mile away near the Lodge. The Lodge area also has a tiny playground, which is near the Lodge Trail trailhead.The park has four trails to hike including the Backbone Trail, which is 1.4 miles and the 1.1 mile Lodge Trail.
When entering the park, you'll pass under the Harmon Tunnel which is the only highway tunnel in Iowa. After the tunnel, turn right and you'll find parking on either side of the ford. On Google Maps, the parking is lot is labeled Pammel State Park Canoe Access Parking.