The best thing to do at minimum is to learn preaching chords in the keys that your father uses. If a preacher is changing keys, most times they'll go up a half step - maybe a hole. So you should learn F,F#,G and G#.
If he starts in E, he's probably going to F or F#. Maybe you could get a recording of one of his sermons.
I know I need to learn more keys for shouting but where I'm at, we don't hoop the traditional way so I really don't have to chase anyone down on the keyboard.