Just so you know, if your intent is to communicate with other people on the ship, we took our cell phones simply because we had them for our Florida trip, but we also took two-way radios. We didn't want to burn our weekday minutes, so we bought the radios -- they worked GREAT for us!
We were afraid there would be so many other people using them that it would be hard to carry on a conversation, but the 14 channel model was more than sufficient. More channels were clear than were being used. We'll never go to Florida again without them.
I'd go ahead and try the radios, and if they don't work, use your phones. BTW, in case you didn't know, they have Disney radios now! We would have bought them, but our radios were a gift, so we
reluctantly took them along! lol