I finally went back to the dealer to ask for help on this. Now I better understand zmao's reply.
In addition to setting the seat memory using the buttons (this locks in your base settings), iDrive also remembers your last settings. For example, you may have made slight adjustments during a long trip or lent the car to someone using your FOB. The memory buttons get you back to your starting point if needed. Apparently each FOB needs to be individually set up so that it automatically changes the seat position the next time that you unlock the driver door. Go to MAIN MENU / SETTINGS / DOOR LOCKS / and then make sure that LAST SEAT POSITION AUTOMATIC is selected. Then get out, lock the door and repeat the process with the second FOB. In my case I set up my wife's correctly and just assumed that the setting was good for both FOBs. After I went through the process with my FOB everything worked fine. Not intuitive but now that I have gone through the process it makes perfect sense. Having iDrive remember seat, mirror, AC temp, radio station, etc is a great feature.