My family (me, DH, DS--9 y.o., and DD--7 y.o.) are going on a cruise around the Mediterranean. I would love any hints you could share as to what to see each day while we are in port. We will have about 6 hours in each port with the exception of Greece which will be 12 hours.

Here is our schedule:
depart Genoa, Italy
Naples, Italy
Catania, Italy
Corfu, Greece
Dubrovnik, Croatia
end Venice, Italy

Thanks so much for any advice, opinions, etc!

I hope that you have more than 6 hours in Venice as you can't begin to see it in such a short time. Besides things like the newly rebuilt opera house and St. Mark's Square, you should consider seeing the art museum that Peggy Guggenheim created in a former palace. There is a tourist center at the train station where you can get deals on things like cheaper tickets for the water taxis and discounts for multiple museums. Go to Murano, the island where most of the blown glass is created. They also have a museum on the history of glass and some of the pieces are more than 2000 years old. And don't eat at the tourist places...find the little hole in the wall places where the locals go for better prices and better food.