Uniworld – Castles Along the Rhine

My husband and I (early 30s) are planning our honeymoon for next year and we know we want to do something in Europe (max 10 days so the pre and post cruise extensions aren't an option for us). We are looking into a Uniworld River Cruise, specifically Castles Along the Rhine and are looking for any feedback that anyone might have. We know about the crowd being older and have no concerns with that. We mainly want to make sure we are using our time in Europe wisely and aren't sure if this is our best option or if we should considering picking one place to stay rather than visiting several places on a cruise.