Help me solve this Macbook wifi mystery
This is not an issue that I have ever seen before. A Macbook automatically connecting to a secured network is something out of a science fiction book.

 As for your sons iPhone, type your subnet mask into your address bar and mess around with the settings for you WEP Key and add his iPhones mac address to your router settings. This should enable your router to talk with your sons iPhone in this case that it is not connecting.

You can also go ahead and remove the network from his phone by forgetting it, and re-entering the credentials for your router in again manually so it can have a fresh start at trying to get to know your sons iPhone connection. My iPhone has trouble recognizing my iPhone sometimes and adding the mac address to my router settings fixed the issue but I am more experienced with stuff like than than your average Joe so try and "Forget This Network" and see if that works if not, try the first option. If all else fails, give Apple a call.