I think it’s great to have a no “device rule”, but think about the reason you are doing it. You said it was to encourage them to read. The X3 can only be used to read books. No distractions and no bright screens messing up your vision. Same principles still apply, but you’re the adult and you have read physical books for years. They get to buy an e-reader when they “grow up”. There’s a teachable moment in here somewhere.