I am not sure how you hunt, but if you hunt from a stand, I would look at the .243 for whitetails. Get a heavier than normal stock, and bump the weight of the gun up to about 9-10 lbs or a little heavier, and there should be no recoil felt at all. Though heavy for all day carrying, it shouldn't be too bad for you to carry to a stand for your dad. I have seen a few deer taken with the .243, some in the 150 lb class, and it handles them no problem.
Just a thought.
Marcial