You could open a screen session and run reaver in it.
screen -S 'name_of your_session' - Starts a session with that name.
You would run reaver and hit Ctrl+a+d to detach from the session, this will run even when you are logged out.
To resume the session, just use the command: screen -r 'name_of_your_session'.
For more information on the screen command, here is the manpage: http://www.gnu.org/software/screen/manual/screen.html