Boy was I wrong. The Carnival Splendor is a great ship. It is only 18 months old. It is the top rated in their fleet for friendliness, and it has received the most 100% ratings from the Federal Inspectors. The ship is immaculate. Our cabins, 1st deck, ocean view, were larger and nicer than our comparable cabins on Royal Caribbean. It was a very good value. My sons, 14 and 18 had plenty to do. Out of 3,500 passengers, about 1,000 were under 18......but we didn't feel over run by kids. The service was excellent and very friendly. The food was good on the Lido deck, and very good in the Black Pearl restaurant. My only complaint was that occasionally some of our side orders arrived cold.
Our ports of call were Puerto Vallarta (very nice, decent amount of time in port), Mazatlan (nothing too spectacular), and Cabo San Lucas (excellent destination, but only 7 hours in port).
I would recommend this to any family. It would be comparatively entertaining to a week at a Club Med.