Hm, what do you mean by "extremely limited and supervised"?

I think absolute 0 is best for as long as possible. If you never introduce them to the drug, they'll never have the craving for it.

That's obviously difficult, practically, and we like movies, so we'll watch about a movie a week... but even I feel that is too much.

They’re 4 and 3, currently it’s probably 30 minutes every other week for the older one. She doesn’t really ask for it yet, just a treat when we feel like it. We’ll also use them on the odd occasion we’re doing long travel.

If you’re including regular TV, sounds like you are, they watch significantly more of that. At least some daily. I don’t think it’s nearly as damaging or addictive compared to phone/pad. It barely holds their attention a lot of the time and they would rather play.

parent-to-parent: this is slippery slope territory

just imo, I can't control you. God bless your family :)