If they are using the wireless headsets than you can listen to what you want via the vehicle's speakers. When our kids are watching a DVD we adjust the fader full to the front so the volume isn't louder than necessary (they've complained they can hear our music over their headsets since we don't allow them to turn the volume up very much).
I assume the '11 is the same as our '10. RES over the heaphones and you can listen to a different source over the front speakers. If the radio detects that the front and rear are on different sources it goes to this mode automatically. If you are listening to the DVD over the front also, you could fade the speakers to just the back. I think these are your choices.