Just a caution for you concerning possible impacts to your Dad's line or the upgrade donor line for others doing an upgrade swap.
Often when trying to complete the upgrade swap and depending on the skillls of the rep completing the activation steps on the assigned line. In this case it will kill your Dad's current SIM and break his voicemail leaving him without a working phone. He will not be very happy if this happens while he is traveling.

This type of error will also make the SIM in the new iPhone unusable on your line since it was already associated to your Dad's number. In this case you would need another SIM for the iPhone 5.
It happens every year, while not a 100% failure rate it does happen and there will be threads about this type of fallout from using an Upgrade Swap. It is always best if you have all devices and individuals together when you do and Upgrade Swap by calling Customer Care or going to an AT&T Corp retail location.
Dave