I agree. Attempts to dictate behaviour in this fashion rarely work... and, as been said, phones are useful to coordinate, and in some cases even find lost kids. (Of course, if you lost track of your kids because you were reading email, that's a whole other issue...)
People will learn, though peer education and self-awareness, how to integrate gadgets into their lives. And if not, there's always that Grand Theft Auto IV radio commercial about being everywhere and nowhere.
