A toast!
What's Father's Day about if not raising a glass to dads? Even if you can't be there to toast in person on Sunday, some of the below will still surely be on the bar cart (and in your father's nightcap routine) the next time you visit.
-Spiffier-than-he'd-buy-for-himself bitters
-A handmade recipe book with a couple of drink recommendations
-Fancy-pants option: A hand blown decanter