Playing on Dvd and using code for steam

When i get the Game in box form could i play using the disk, and download through steam using the code for steam so my son can play via steam at the same time why i play using the dvd.as if he is using steam he would not need the dvd.or if activated by steam does this stop the disk working

You were given an answer in your other thread. What you are proposing is against the license conditions.