Your parents should be able to use a Northwest club in Newark. Just tell the gate guard that they are connecting to interlational business class in Detroit. I have never been challenged in Memphis flying first class to Seattle to connect to the Narita flight. Also flying upper deck is only worthwhile in the 747-200s because you get to enjoy the old first class area. In the 747-400s, it is better to try and get in the nose, which was the old first class area in those aircraft.