For a hook, you have to close the "clubface" by really turning your grip on the controller to the left. I was doing this initially, but you really have to maintain this grip throughout the swing to get it to hook. I was confused by the "ball spin" feature that is a separate control that affects the ball spin one the ball lands (I think).
If I ever get my 7 year old son off the Wii, I will investigate further!