Hi, My wife and daughter are on TD visa. I am on TN Visa for last year i.e., 2015. We dont have ITIN for my wife and my daughter. I want to file extension.

They are currently visiting outside USA. Can I file ITIN on behalf of them. Also how to file extension? What is 6013 g form ? Can I use 6013 g for my wife and my daughter ? Do I have to use Form 4868 or both  forms? Thanks