We took our 4 year old and 8 year old snorkling at the stingray and coral reef in Caymans in December when we were cruising on the Liberty. Please be aware they do not have small snorkle gear for kids despite Carnival promoting it for kids. My yongest and wife stayed on the boat and my 8 year old just swam but didn't get to enjoy looking underwater. We complained to the Excurision desk...they have a "too bad, so sad" policy and act like it is between you and the excurions company. We will be writing carnival to get some of our money back. If your kids swim, that's good but take kid goggles with you. Otherwise, it's should be fun! As for Camp Carnival.....it was awesome. The kids kept asking to go back. We even felt comfortable enough to leave them there while we went on an excursion in Mexico. However, your 7 and 9 year old will not be together. There is no discretion since they break them up by age group.