He can easily purchase the required chip for an iPhone 5 at any of the service providers Orange/Claro/Viva/Tricom. This will be a simple phone card and he will use the phones internet capabilities in wi-fi areas. You only have to show him how to join protected wi-fi providers ie password. Orange also sell data plans with out a contract but using wi-fi only is much cheaper.
The iPhone is intuitive and will be no problem. There's also a Mac store near him if he needs help after my umpteen hour tutorial.