In C.S. Lewis's The Lion, the Witch and the Wardrobe, is Edmund chosen or fated to be the betrayer of his family?

From the beginning of C.S. Lewis's novel The Lion, the Witch and the Wardrobe, the character Edmund is presented as difficult. As the story opens, the four children have been evacuated from their family home because of the war. They are sent to the remote country home of an old professor and quickly conclude that they will have ample opportunities for exploring and fun. Edmund, however, is noticeably different than his three siblings. Early in Chapter I, as the children are contemplating their new surroundings and the older children, Peter and Susan, are assuming the roles of adults, Edmund angrily responds:

"Oh, come off it!" said Edmund, who was tired and pretending not to be tired, which always made him bad-tempered.... "And who are you to say when I'm to go to bed?"

Lewis's novel is, as readers know, an allegorical children's fantasy heavily steeped in biblical prophecy. As such, when one considers the motivations and actions of particular characters, the question of predetermination invariably intrudes. This is the case with Edmund. Is this young child fated to act the way he does, or is he chosen? If the lion, Aslan, represents Jesus Christ, then one can logically argue that much of what occurs in Lewis's story is preordained. In Chapter IV, Edmund encounters the witch, who inquires as to whether the boy is a "Son of Adam" and proceeds to interrogate him. Hostile at first, the witch senses in Edmund an opportunity to exploit the child for nefarious purposes and, instead of offering this Son of Adam an apple, she provides him the Turkish Delight, a baked sweet, he has requested.
So, Edmund is enlisted into the services of the witch, the obvious stand-in for Satan, and agrees to betray Aslan, just as Judas betrayed Jesus. Again, though, the issue of "chosen" versus "fate" is complicated. In Chapter VIII, Mr. Beaver observes of Edmund, in conversation with the other children:

"I didn't like to mention it before (he being your brother and all) but the moment I set eyes on that brother of yours I said to myself 'Treacherous.' He had the look of one who has been with the Witch and eaten her food. You can always tell them if you've lived long in Narnia, something about their eyes."

Edmund has displayed the qualities of one capable of acting terribly on his own and could be considered ripe for recruitment by the Devil. That he does, in fact, act in the service of the Devil before finding a measure of redemption suggests that the answer to the question--is Edmund chosen or fated to be the betrayer of his family--is both. His hostile nature lends itself to exploitation by those who would do so, such as Satan. In the context of Lewis's story, it could be considered both Edmund's fate that he would be chosen by the witch/Devil to act on her/his behalf.