I recruited the mages circle to help slay the demon and free the boy in Redcliffe without killing his mother. However after I have gone into the Fade and killed the Demon I got a cutscene showing the mothers funeral voyage and the code article was updated to say that the Arlessa gave her life to save her son. Yet both the Arlessa and her son are both very much alive and I can talk to them. Hopefully this is only a minor bug that won't bite me in the ass later. It is a slightly annoying end to what was a truly epic quest chain.
By the way I chose to send Joran into the Fade - It seemed only fair given his role in causing the mess. He has a good set of spells with useful buffs and good damage potential so it was an easy enough battle against the demon.