Good luck! I think you can encourage it, but until their mother steps up, it will be hard to "demand" no tech.
This past weekend, we towed the pontoon 7 hours to my husband's daughters' place to spend a few days out on the lake. When the 13 year old stepped on the boat with only his phone in his hands and a panicked look on his face over where to safely place it in close proximity. My husband told him he wasn't going to watch him clutch that *^$@ thing all day. Showed him the dry space we keep ours (out of sight and mind) And told him to leave it there. The kid was happily occupied all day with fishing and swimming ... only asked about a phone to take a picture of his fish. The parents on the other hand, checked theirs ever time it made a noise or it flashed through their brains that it had been 60 seconds since they checked it last.
So I repeat the previous suggestion...keep them near water!!!!!! The thought of losing that "life-line" long term will be enough to get them to put it down a bit.
