Rome to Athens: What excursions not to miss?

We just signed up for a Rome to Athens cruise on the Windstar Ship with stops in Sorrento, Lipari, Giardini Naxos, Gythion, Monemvasia.

What are the sites and excursions not to miss?

I think we will take the ship's excursion from Sorrento to Pompeii because it is quite a distance and I get nervous about being too far away from the ship on an independent excursion. I do wish that we were staying longer in Sorrento because I would love to explore the town.

We are open to private tours at other locations. The Windstar event is on Giardini Naxos in the afternoon, so we may not do much that day except explore the nearby town in the morning (Taormina) .

If any of you have sailed on this route, I would love to hear your impression of it and your favorite stops. This will be our 6th cruise on the Windstar line!

Yes, take the ship excursion to Pompeii. We were going to take the train on our own, but the schedule didn't work.