Ok, so this is an ethical "brain teaser". I've heard a similar one where there has been a car accident and many people have been injured including your mother, the love of your life, and someone else's baby. When the ambulance comes there is only one seat left and (for some reason) you have to choose who is saved.
Most people choose their mother, in my experience, because of the blood bond. But if you change the scenario so that the baby is your baby, then there is no contest and everyone chooses to save the baby.
In the case choosing to save either my father or my child, I'd save my child. There are two reasons: First, my father has had a chance to live his life and, second, the bond between me and my child is stronger than any other kind of bond. I don't think most people would hesitate, really.
Plus, a father would understand.