We are arriving in Frankfurt/Mainz on August 29. The rest of our tour group arrives the next day, so I would like to plan a day trip or short Rhine River cruise before the tour starts. I think we will go straight to Mainz, check in at hotel and do a little light sightseeing in Mainz on the 29th. What would be the best plan for us to see a bit of the Rhine? I have heard take the cruise up and then train back to Mainz. Suggestions?