Hello everyone: Apologize for the late reply and sincerely appreciate for all your input and ideas! Have been terribly busy for the past few weeks. After researching for more options plus with the release of coming Apple iOS6 (activate Siri simply by pushing the navigation button on the sterring wheel), we decided to go with Medcedes ML350. Currently waiting for the release of 2013 model which should come out in the next month or so. Again, thank you very much for everyone's recommendations, and enjoy driving! :)
p.s. Keep fingers crossed if the 2013 M class will make the 3rd row seat available as an option (rumors), but I doubt it's gonna happen.