Is your Dad a young 80? I think it's important to take into consideration the reality of your Dad's abilities to care for a Yorkie.
I commend you for your forethought of the inevitable for when your Dad passes and what plans would be set up for his companion.
It would curl your hair to know how many family members do NOT think twice of dumping the dogs afterwards or worse yet have them put to sleep.
Also, have you considered another breed that might be more suitable (larger) for your Dad? Yorkie's can be easily tripped over and for your Dad to suffer a broken hip at his age would not be good!
Good luck in your search...
