The Ohio River Museum is about a three-minute walk to Campus Martius Museum of the Northwest Territory, so they should or could be done in the same day. You can park at one or the other and walk to the other.
The Ohio River Museum has three building (you walk between each building) and many items to look at on the grounds. It tells the history of the Ohio River and the travels down the river. The museum is filled with models of paddle-wheel boats, steamboats, and boat parts. You learn about how boats traveled down the river with passengers or supplies. The museum not only tells about boats on the river, but also the ecology of the river. What is nice about the museum is you can take as much time as you like looking at each photo or artifact. The museum does not feel rushed. There are lots of great models to look at. There is a very informative movie in the museum.
Outside of the museum there are a few boats that would have traveled the river. One is a working steamboat called the W. P. SNYDER JR. You can take a tour of it. You can also take a river cruise on the Valley Gem for a cost. If you want to take a cruise you will need to plan ahead to be there at the right time. The Valley Gem does lots of kinds of tours so check out their site.
This museum might not be for everyone, but is does have some very interesting exhibits. Give it a try.