You didn't list what ports you will be at but if you are going to Florence is here information on a very good guide there.
My wife and I were on the Golden Princess this summer and did a private tour with 3 other couples with a very good guide, Paola Migliorini. She met us at the ship in a new clean van with good A/C. We asked to see both the highlights of Florence as well as Pisa and she managed to work both in during our 8+ hours we spent with her.
Paola did an excellent job of arranging ahead of time tickets so we could see Michangelo's David without spending an hour in line. We were able to get a chance to see many of the major sites in Florence as well as seeing the Leaning Tower of Pisa on our way back to the ship. She allowed us an option for lunch that gave different members of the group an opportunity to see or do a variety of things which I felt was an advantage over a more formal lunch arrangement.
Paola lives in the old town section of Florence so she can get her van very close to attractions as opposed to the bigger tour buses that have to park at the parking lots on the edge of town and walk in.
One of our tour members wanted to do a wine tasting and Paola was able to arrange that event while allowing others who didn't feel like wine some additional free time on their own.
All in all it was an excellent tour and Paola did an excellent job as our guide.
Hi ,we were on the Millenium and we would recommend that you try and get on the walkamalfi tour of Pompeii and Amalfi Coast when you dock in Naples. firstname.lastname@example.org. It is a full day private tour with two hours at Pompeii and then a wonderful day touring the Amalfi Coast.