I think it's great that your Dad likes horses and wants to take up riding with you. It's something that'll make you closer. Has he ever ridden before?
He may have once or twice, but he's never had any formal instruction, and couldn't do it on his own right away. He really seems to get into it though, and has always wanted to have a horse farm of his own. It's what he wants to do when he retires. (Not that I'm complaining! I'd go up with him and run it for him, and teach him as I go!) But he seems really interested in any horse stuff that I tell him. He just wants to trail ride, but he'd learn all the proper basics. But he told my trainer: "I don't want to do any of that fancy stuff!" I'd really laugh though to see a 6'2 man of my father's bulk attempt dressage..... Roping or cutting, sure. :-)