We took a 4 night, 5 day cruise for our daughter's 5th birthday. We specifically took a shorter cruise because it was her first cruise. We chose Carnival after reading countless reviews on their children's programs versus other cruise line's kids programs. Carnival went above and beyond our expectations when it came to the programs for her. She loved them so much she ate lunch and dinner with them every time she could. She never ate with us in the MDR! The children's staff was amazing and we tipped them generously the last night of the cruise. We would call (on the cell phone they gave us or from our room) to ask if our daughter wanted us to pick her up and the answer was always "no". She still talks about the cruise to this day. She loved room service for breakfast, the water slide on the ship, and all the fun things she got to do in the "kids club".
As for my husband and I, we have cruised before and some things weren't as nice as other ships we have been on. The buffet for lunch took forever to get through because of the configuration. The sushi cart in the casino (odd place to put it!) had a 20 minute wait and then they rationed out four pieces of sushi roll per person!
On the plus side: the cabin was very spacious, our daughter loved the towel animals each night, the spa was great and the fitness center was clean, well equipped and the staff friendly. Overall the staff on the ship was amazing and very helpful. The kindly delivered my daughter's birthday cake to our cabin since she didn't go with us to the MDR the first night at sea.
We are cruising again this year (with HAL) for a Christmas cruise and we can't wait to go! Cruising with WELL BEHAVED children is fun and enjoyable for everyone!