It would be a really good idea to make sure you know what dances your dad is comfortable with. If he is an experienced dancer, then I would advise the "slow" waltz (slow vs Viennese, which is fast). All male dancers are told that our job is to make the woman look good, and I think that is easiest for the leader to do (especially with an inexperienced partner) with the waltz.
Good luck, and remember, mistakes dont count! The goal is to have FUN!!!