It really does depend on what you and your family like. We've been to all of those locations except Santorini and Chania either on a cruise once or twice or in some cases for a few days in addition to the cruise and enjoyed them all. If you've not been to any, then either research the individual locations to get a sense for what you'd do if you were there and which appeal the most to the family or pick the cruise which best suits your schedule. We'd obviously pick the second because it has the two locations we've not yet been to but either one can be great if you know what you want to see or do.
We've cruised twice to Civitavecchia and did a tour to Rome (saw Vatican museum, St. Peter's Basilica, Trevi Fountain, Colosseum, lunch at a hotel downtown Rome) and once took an excursion out to Orvieto (hilltop town the opposite direction from Rome from Civitavecchia). We've also spent four days in Rome with a side trip to Orvieto. I'd go again in a heartbeat to both - there was so much we didn't see in all of those times.
We spent several days in Barcelona both before and after two cruises and loved it. Definitely planning to go back and spend time there. We did walking tours, museums, Parc Guell, food (!!!!!), church tours, spent time at the pier, short trip to Monserrat, a food and wine tour outside of Barcelona. Fabulous time.
Our ship stopped in La Spezia twice which is reasonably close to Florence and Pisa and very close to Cinque Terre but I think
DCL now goes to Livorno instead. Once we went to Florence and went to the Accadamia to see David with a walking tour around Florence. The second time we went to Pisa and climbed the tower and wandered around the Piazza. That's a much shorter trip - other than that, there's not much to see there but we really enjoyed it. We stayed in Florence for three days a few years ago and went to as many museums and historical buildings and art galleries as we could manage in that time but I still need another few months there. Cinque Terre is much closer to La Spezia (7 minutes by train) than Livorno, but IMO, although Cinque Terre is amazing, I think you need to stay there a few days to really appreciate it rather than a day trip.
We stopped once in Naples and did a tour that included a climb up Vesuvius, lunch and tour at a winery on the slopes and a half-day at Pompeii. We later stayed in Sorrento for four days and took the train into Naples most days (Naples itself is not very nice) and once again climbed Vesuvius, spent the entire day at Pompeii and a half-day at Herculaneum. I'd do all three again plus there are some museums there I'd like to visit plus several other historical sites. One day we went out to the Amalfi coast from Sorrento which was fabulous. We still haven't managed Capri. I will go back to Sorrento again.
I'm assuming the Cannes stop is actually Villefranche, which is close to Cannes, Monaco, Nice and Eze. We skipped Monaco and Cannes - nothing of interest to me there. We did two trips to Eze - one was to Eze and Nice where we toured around a bit and did a wine and cheese tasting. The second time we went to Fort de la Revere in Eze where we hiked throughout the park and ended it with a French-style picnic (local cheeses and meats, freshly baked baguettes, salads, and wine in the park on large blankets - just lovely and delicious).
We've done one trip to Mykonos where we took a tour out to Delos Island for the ruins and museum. Afterwards, we just wandered the town a bit. There's not much to see and do there other than Delos unless you're into very rocky beaches. My aunt just loved Mykonos and used to go there once a year for a long period of time but she spent her time on the beach which isn't our thing. But I think you need to see Mykonos at least once to appreciate Greek and Mediterranean history. Although I probably wouldn't get off the ship there again, I'm very glad to have seen it. Maybe I might go for a glass of ouzo at a cafe. Maybe some food. Maybe back out to Delos to refresh my memory.
Santorini and Chania are on my list. I want to see the bronze age ruins in Santorini and I want to see as much as possible and there's just so much to see on Crete I don't know where to start.
