Unfortunately yes if you use gamepad you cannot use other controllers on Wii games. You can say no if it asks do you want to use gamepad then you use multiple controllers other than gamepad, but if you use gamepad you can only use gamepad.
Wii is like the most restricting console on controllers.
that really sucks. I mean its good if your playing by yourself. but sucks if you want to play against some one. Even worse that its only the game pad. Not even the pro controller. Thanks you for you reply, cause i was really going crazy.