Great thread. This was my concern, and I had to bring it up with the family. The consensus is we don't want to be rushing from an excursion to get ready for dinner. The other concern is that we eat so much at the port that we are not hungry at 6 pm when we return to the ship. That said, we are not late diners, and I cannot see myself still at dinner at 10 pm after a long day at port.
We are on the 9-Night Mediterranean with Greek Isles Cruise. After booking our excursions, only one is scheduled to push our early dining, which is the Florence/Pisa excursion (as mentioned above). The early dining may still work out.