As far as Maggie goes, first there will be this conversation :


Luke: How did my father die?
Obi-Wan: A young Jedi named Darth Vader, who was a pupil of mine until he turned to evil, helped the Empire hunt down and destroy the Jedi knights. He betrayed and murdered your father. Now the Jedi are all but extinct. Vader was seduced by the dark side of the Force.


Followed by this conversation later in the series :


Luke: Ben! Why didn't you tell me? You told me that Darth Vader betrayed and murdered my father.
Obi-Wan: Your father... was seduced by the Dark Side of the Force. He ceased to be Anakin Skywalker and "became" Darth Vader. When that happened, the good man who was your father was destroyed. So what I told you was true... from a certain point of view.
Luke: A certain point of view?
Obi-Wan: Luke, you're going to find that many of the truths we cling to depend greatly on our own point of view. Anakin was a good friend. When I first met him, your father was already a great pilot. But I was amazed how strongly the Force was with him. I took it upon myself to train him as a Jedi. I thought that I could instruct him just as well as Yoda. I was wrong.
Luke: There is still good in him.
Obi-Wan: He's more machine now than man. His mind is twisted and evil.
Luke: I can't do it, Ben.
Obi-Wan: You cannot escape your destiny. You must face Darth Vader again.
Luke: I can't kill my own father.
Obi-Wan: Then the Emperor has already won. You were our only hope.