Idea: Apple Authorization to Charge paperwork
Here's something to try, which is 100 percent legal and well-supported by Apple.
Call the Apple Store where you want to make the purchase. Ask for a form called an Authorization to Purchase (or something like that; I'm going from memory here). These forms are individualized for each Apple Store, so you have to get it from the one where you want to make the purchase. The business manager there should be able to give it to you, or even send it to you by fax or by email. This is standard stuff for them.
It will ask for your Dad's credit card information, signature, maximum amount to purchase, etc. It will also ask who will make the purchase. Your Dad will need to sign it, but he can send it back to the Apple Store by fax, since (as you said) he is out of the country. You will need to show a form of ID when you come to the Apple Store.
It should be very easy to accomplish. This is completely standard stuff, if your Dad has access to a fax machine and is willing to help accomplish this. It's not difficult to do at all. I would try to do it today or tomorrow, because I'm sure that the business managers at most of the Apple Stores will be swamped with work at the end of the week, getting ready for the iPhone 3G launch.
Good luck! Just a suggestion......