my dad had me beyond the age of 40, i think its fine. sometimes its kind of depressing for me considering that i wont have as long as a time to be with my father, and i want him to be able to hold his grandkid once i have one. so from the perspective of someone who is in the situation i think as long as your dad is an active guy who can handle a kid, like mine can, there is nothing wrong with it apart from some harsh realities.