Hi! We just got back this week from Carnival cruise to W. Caribbean and took my 2.5 year old daughter to StingRay City Sandbar. She absolutely loved it (loved seeing & touching them and even starting calling them her buddies). She is still talking about it and I must say that it was the highlight of our whole week. I can understand why there might be some hesitation from others, but my daughter LOVES animals and has been to Sea World and several zoos/aquariums where she has been able to interact with sea life.\ So, we were pretty confident she would enjoy it. If your children likes animals/fish/etc., then you might be OK, probably depends on how adventurous they are, or how easily scared. The waters are very shallow (about 4 ft.) so you should be OK holding your little one. We took a "KIRK" Company sponsored tour and they didn't have a problem w/ her age. We arranged it through Carnival, but I imagine you can arrange it on your own if you can't through your RCCL. If you can't work it out to bring the kids - try to go yourself as it is an awesome experience.
Hope that helps and you enjoy your time! Let me know if you have any other questions!
Jodi