Thanks to Pert for the mention of the IDE feature that updates it to handle the Due board. Due software seemed to install OK.
Right now my situation with the Due-Grove base shield-luminance sensor demo sketch is as follows:
IDE shows for Port: COM4 (Arduino Due Programming port).
IDE 'Board Info' shows Arduino Due programming port.
IDE shows programmer as 'AVRISP mkII'.
Due board yellow LED is on and no longer blinking. Green LED is on.
Verify-Compile of the demo sketch is OK.
Upload gives 'No device found on COM4, an error occurred while uploading the sketch.
Please note my USB cable goes from the PC to the Due boards programming port right next to the power connector.
So it looks like I have the Due software installed OK but I'm still missing something. Any comments appreciated.