While you should download it before you are on the ship, and then just launch it once onboard, you CAN download it while you're still at the dock. At least at PC. It didn't use any paid wifi at all when DH and DS were rushing to download it to their devices and then launch it before sailaway.
That's really weird that that happened to you, ovloubet, unless you started after sailaway?
Ds has a decommissioned android phone. Used for music and games. No SIM. But it can get wifi, so we decided to let DS use it.
DS took his device to Oceaneer's Lab and would use it to let us know it was time for us to pick him up (we still haven't been comfy giving him in/out privileges). MUCH easier than getting the CMs to contact us, especially CMs use the horrid Wave phones. Oh and DS was 10 at the time. So at 13, absolutely. What a great way to keep you apprised of his movements around the ship! He'll be at the young teen club where they can come and go at will, so it's terrific to have the app.
As was said, it's not perfect. Users want to turn on their phones and go into the app and check for messages; while I think it's supposed to buzz when a message comes in, it doesn't always do it and doesn't always show that there's a message until you're in the app.
We LOVE being able to see the times of events. If two fun things are happening at once, is one happening *again*? Can we delay that until later so we can do this other thing now? SO much better than waiting for each day's Navigator to show up.