As long as you're keeping your children safe and near to you & you know where they are, I don't think it's dangerous. As you say, if they would freely give their names to someone, I don't think that having their name on a jumper or hat makes them any more vulnerable. Presumably you teach them to say no to strangers etc, even if they know their name, so I wouldn't worry. Obviously I'm not a mummy yet so people can tell me to be quiet if they wish

, but that's just my opinion now.