Sailed on the Carnival Pride to the Mexican Riveria with large family group, including my three grandchildren, ages 1, 2, and 3. We ate most evening meals in the dining room at early seating, and took turns taking the one year old out when he became restless.
Camp Carnival did not work out too well, as the 2 and 3 year old did not want to stay by themselves, even though they go to preschool a couple of mornings a week at home. They did attend a few activities however, and had a good time. I think toddlers need to have a very out going personality to be able to adapt to a new 'care' setting, while at the same time adapting to a new home away from home.
If you have any questions about the Carnival Pride, the ports, or activities on the ship, I would be happy to try and answer.