It seems that Mr. A. Rosich is right. I have a small oblong hole right above the rear door latch that I can see a small mechanism. This must be the child proof lock. There is no mention of child proof locks in my owners manual. I think the button on the center console controls windows only. My kids never have the option of having their windows powered but they can open the door so I would think it only affects the windows.
1994 E320 Wagon (Died @ 308,669 miles)
1995 E300 Diesel (194,000)
1999 E300 Turbodiesel (244,000 miles, dies at 255,000)
2006 Toyota Tundra SR5 AC 4X4 (115,000 miles)
2011 Audi A4 Avant (129,000 miles) hate this car!
BMW 330 xi 6 speed manual (100,034 miles)