We cruised the Iowa River today on the Scenic City Empress Riverboat. The river map gives you an idea of what you see on the cruise. It's a slow pontoon boat ride that takes 1 hour 15 minutes in total. The upper deck has sunny seats available and the lower deck has benches and tables.
We moved downstairs when the sun became too hot, which worked well because my kids were getting bored, so they did activity books on the tables. They did like seeing the swinging bridge which we had crossed just before the boat ride. It's accessed via Assembly Park, which has a great playground.