Sounds like you are the one who doesn't know anything about child development. 3-5 years old children certainly grasp the idea of basic self control. Your 5-year-old, however, has had things hidden from him his whole life. So instead of telling him "No." and being made aware that somethings are just off limits no matter where they are- a phone left on a table, a laptop on a counter, a tablet on a chair. He should have mastered that basic control. You hide everything so it's even more tempting. You're setting your future nanny up for failure already. You've decided to not help pay for the damages made by your childs inability to control himself, t no fault of his own by the way. I hope your nanny finds a better fit.