US citizen. 34 hours layover on a cruise.

I am a US citizen. I'll be on a cruise, it arrives in Shanghai at 8AM and departs the following day at 6PM (34 hours total).
I am planning day tours that take me out of the city on an escorted tour that I intend to purchase from the cruise line (Holland America) 9-10 hours the first day, and 7-8 hours the second day.
1) Do I need A visa? or am I covered by the 72 hour free transit?
2) At the end of the 10 hour tour , am I allowed to stay in town for dinner (without the tour guide) or do I have to go back to the ship immediately at the end of the tour?

Thank you, OM