OK, here is the scoop on the ports you are going to visit.
Barcelona...easy to do on your own. Take the local sightseeing double deckers for an orientation and then walk to whereever you want to spend time.
Livorno...Easy train ride to Florence. Take a taxi to the train station from the ship (you can walk it, but it is a pretty good distance.)
Civitavecchia...train station is within easy walking distance of the port. Once in Rome, take taxis where ever you want to go.
Mykonos...walk into town from the tender port (great shopping) and then taxi to the beach if you want to go
Kusadasi...Don't miss Ephesus!! Either take a ship's shore excursion or grab a taxi and negotiate for 3-4 hours to go to Ephesus.
Piraeus...DO NOT TAKE A TAXI!!! Walk to the train station in Piraeus and then take the train to the Platka. From there, walk to the Acropolis.
Santorini...easy to do on your own. Excellent public bus system to the beach
Naples...train will take you right across the street from Pompei, or take the ferry to Capri for the day.
Check out www.EuropePortReviews.com
on each port for detailed information about what is there.
Have a great cruise!