My son currently has my old 3GS. Would love for him to have a Retina iPhone but he is to young to need data and voice. I was thinking of buying an iPhone 4 once it drops to $0.99, putting him on the family plan at an additional $10 per month and limited data and turn all services off. Is this the best option? I would love to have GPS turned on so that I could locate him in case of an emergency.