Can I display to more than one MFC CWnd (CButton, CStatic, etc) on the screen? If so, how?
Yes. Each CWnd-derived object will probably need a GL rendering context associated with it. Assuming you are doing this on a single thread, as long as you make sure that the correct rendering context is current to the thread, you should not have a problem.
Remember that a rendering context can be current to one and only one thread at a time and a thread can only have one rendering context current at any one time. Keep this straight and there should be no problems.