Sorry to hear about your current situation.

As a practical matter, remember that if you do use your father's miles, you need to keep an eye on the expiration date of the miles and maintain some earning or spending activity in the account to keep them active (this doesn't have to be on flights).

Since you're planning far ahead, the easiest thing to do would be to credit a hotel or car rental to his MP number which will extend the expiration date by another 18 months, or draw down his miles before you use your own.