Da Wife Said No:
You can kill all of them. It was just a test to see if you would kill on command. If you really want to have fun with it....... SPOILER coming..................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................Kill Astrid instead of the hostages. It starts a special quest. Warning: You will not get the Dark Brotherhood achievement if you go this route!!!!!!!
Ill tell you I had my battle axe drawn with her face intended for it, but I just couldnt do it........
Kinda wishing I would of now. That sound fun.