Going on a RC cruise in July to the Western Caribbean. Our family has three staterooms: Mom and Dad (that's us); grown son and wife: grown son, wife, and 2 YO twins. We're all on the same level of the ship. How do people stay in touch with other family members? We won't have use of our cell phones on board. What about putting post-it notes on the doors? How well do walkie talkies work? Any other creative ideas? Thanks for your help!