Not a dad (of course) and no longer have a dad, but we commemorated him by driving up to Idaho City and eating at a place he really would have liked (big servings; biscuits and sausage gravy) but never had the chance to go. My dad also really liked "Sunday driving" before gas got too expensive, so we figured he would have enjoyed the drive up/back too. It combines two scenic routes along wild rivers....Unfortunately a lot of other people (well, by Idaho standards) seemed to have the same idea, so we ended up in a minor traffic jam at one point. In the middle of nowhere--there's not even a cell signal--so figured there'd been a car wreck, or maybe Search and Rescue was responding to an incident on the river, but it turned out to just be people waiting to make a left turn onto the road back to Boise!
After a very big breakfast, burned it off with a two-hour trainer ride at about HIM intensity under-overs). Planning to get in 15 minutes or so on the rowing machine in a little while--it seems to help work out kinks with the elbow.