I agree with all the points made by previous reviewer for Liberty. Selecting the dates for short, inexpensive cruises is crucial. The EU has many school holidays and Easter is prime time for vacation - 3 weeks of holidays for Spain! So, we expected the crowds and were fine with that.
Families seemed to enjoy the ship amenities and the food (yes, it was very casual and not very fine dining but we were OK with that). We were a party of 7. We ate early and had no problems finding tables in Windjammer. We also used the on-line pre-cruise planner about 30 days in advance of the sailing, and had no problems getting shore excursions, spa treatments or seats for shows.
We were very lucky and had no smokers in our section of balconies.
1. Barcelona: DIY. We stayed pre/post cruise at Eric Vokel BCN Suites. Very secure and spacious. Easy 10 min. slow stroll to Sagrada Familia where there is the metro and hop on/off buses and tourist info centre. Receptionist booked taxis to get us to the port. Taxis came promptly and cost about 25-30 euros.
2. Villefranche sur mer: Lovely port. Tender was well-organized. Part of our group booked a shore excursion to Nice/Eze (fairly strenuous hike in Eze), but others took the train to Nice. Uphill climb to train station but directions are well marked. May 1 is a national holiday so no buses or trams available in Nice. Ship's excursion was best bet in this case.
3. Rome: booked Rome in Limo. Very prompt pick up at Civitevecchia. Worth the money and follow their website's advice regarding advance purchase for entry at the Vatican and Colosseum. Take the original print of the on-line tickets with you. The scanner at the Vatican and Colosseum will reject photocopies. We booked the cheapest guided tour of the Vatican Museums (group was only 15 people at 2 pm). Do your homework and read about Rome ahead of time.
4. Cagliari: Took ship's shuttle to the info center at about 10 am. The shuttle was greeted by sellers of tours (Segways, open air tour buses). To get to the green "cagliari tour" bus, you need to walk about 20 minutes from the info center, then uphill to get to the main piazza to catch the bus. There was a 2 hour waitlist list for the bus. This company only has two buses. So, we went back to the info center and found a taxi to take us to four sites for 50 euros. If you have seniors in the group, it is probably best to stay on ship.