I want my son to be able to message me onboard the ship via the Navigator app. Does he need to have his own Disney account to do that? I know that the app's appearance and functionality changes completely when connected to the ship's wifi. Perhaps being on ship wifi allows him to skip the Disney login and instead he does something like (1) enter our stateroom number or reservation number and (2) select his name, which then allows him to use the app??? I just don't want to take the chance that I needed to do something in advance to set him up. We may end up using Wave phones anyway if the Navigator App isn't good about sending push notifications for messages. But Wave phones are clunky and I'd at least rather have the option.