My issue isn't with web enabled devices connecting via wifi. It's easy to set up controls, and whilst some kids might get around them, I doubt mine will as they are 8 and 9 years old.
The issue I have is the youtube app on my Tivo box can not be password protected. Virgin Media used to allow me to put a pin number on it, and now I can't. If I could stick a 4 digit pin on it that would solve my problem.