You will love the cruise!! We did the
DCL 11 night Med cruise in May 2010. For most of our shore excursion we booked private tours. we did not book through Disney because it was cheaper.
We were a group of 4 and we meet up with family of 3 (we meet them on a the Dis board) and split the cost of the tours. Private tours can normally accommodate 6 to 7 people and the cost is a flat fee for the car. For example, 10 hour tour of Rome cost 500 euros divided by 7 people cost 71 euros per person. Also, having a private tour we got to skips some line at the Colosseum and other places.
Maybe this group will share private tours. Some people did the there own tours of the ports and other went in groups (joined with others on the Dis board) for safety in numbers.
Keep in mind the port and the location can be hour(s) away. For example, it takes about 1 - 1.5 hours from the port to get to Rome and about an hour to get to Florence.