It can be an adjustment for sure. But I think most people find that they adjust pretty quickly. There is a lot to do on the ship and the time goes by pretty quickly. Unlike DW, service won't be cutting in and out, which can actually make it easier to stop missing it. Plus, before they know it they will be back at the airport and can "catch up" on what they missed, but by then they may be more interested in looking back at all the great stuff they just did.
Also, there are plenty of things you can still do with your phone. Take pictures, write up trip reports, use the Navigator to plan upcoming activities on the ship, or check out tomorrow's menu. Or send messages to other people you know on the ship so that you can meet up and do things together. We were a group of 9 and we chatted back and forth quite a bit about ideas of what to do, and mixing and matching in different groups to try different things.
I'd say it seems worse than it actually turns out to be, so the less they can think about it ahead of time, the better off they will be.
You have to work pretty hard to be upset on a cruise.