You should be able to attach the additional meshes, by parenting them to the bone that moves the head. As long as you don't replace the mesh, i reckon it should fine.
But, it also depends on what tools your using :o) You might be able to do this easily in your modeller/animator :o)
But, it also depends on what tools your using :o) You might be able to do this easily in your modeller/animator :o)