This was my 5th cruise but first time on Disney. All the other 4 times were on Carnival ships. While I would not go on Disney without kids, it was great for people that are cruising with kids. We brought our 4 year old and he had a great time.
The service was world class and they do cater to children but still take care of the adults too. The food was average for a cruise, some of the best things were the chicken strips for the kids and the beef tenderloin for the adults. The only thing that we didn't even finish was the turkey in the Triton restaurant.. it was dry and chewy... like rubber. Our son's favorite was the self service ice cream machine on deck 9.
Our son went to the kids club about 6 times and he had a great time. There is a small on-board arcade called Quarter Masters that our son liked to play in but it is small and some of the games were too big for him like many of the driving games, he couldn't reach the pedals. Also, on the last day of the cruise about 1/3 to 1/2 of the games were broken.
As far as the ports, we stayed in the popular areas and off the small side streets knowing that Mexico has some problems right now. But we did visit Senor Frogs in both ports and did some shopping. We also took a water taxi to Lover's Beach on Cabo San Lucas so that our son could swim. It was the cleanest, clearest water I have ever seen and he had a great time. The weather was great. Each day was sunny and warm (75 to 85) and we didn't hit rain until we returned to Los Angeles.
If I was to compare Carnival to Disney, I would say that Disney is much better for kids. Carnival is better for the adults who like a party cruise.