My dad now knows that I own guns. Actually I should say he knows I own *a* gun, since I made sure to use the singular term. My mom has known for quite some time that I own guns and go shooting at the range and she has no problem with it. My dad is not so reasonable or rational. I think he took it well. At the least he took it as well as one could expect an anti-gunner to take it. A few years ago when I wanted to buy a P22 he absolutely flipped his lid when the issue came up, so compared to that this went extraordinarily well.
He did express what sounded like at least passing interest in going to the range with me. To be honest the thought of my dad + guns worries me a bit, but I don't think you can ever really know till you get someone on the firing line with gun in hand.