Help setting up bones for facial deformation

I have created a cartoon character and rigged it using the rigify plugin. I then created my own widgets and made it so that eyes followed them, but I would also like to set up some widgets for animating the face and I don’t know how to go about it. The end result that I am looking for are several, easy to use, objects, that when moved will allow me to animate the face quickly. Any tips on how to get this are welcome. I am stumped. My idea was to create a seperate bone from the rigify rig, and parent just one vertex group to it from the character but how do I do this?