Yeah, an impulsive child from a period of war rationing fell for an adultâs trick. Itâs bad enough to victim blame in this case, but C.S. Lewis so wants this to be the 30 pieces of silver for his Jesus Fursona and it just does not work (just like arms dealer father Christmas and the Liar, Lunatic, or Lord argument.)
For the story to work, Edmund has to be a traitor. But he isnât, and moreover, it is impossible for him to be one.
Second, heâs being coerced and manipulated. The White Witch got to him first., and told him she was the rightful ruler, and she had the accutamonts to back that up. To his knowledge, even if heâs suspicious, his family has fallen in with rebels and keeping the witch happy is the only way he can have the pull to save them. Telling the White Queen about Aslanâs return canât then be a betrayal of them, even if he was old enough that he could be ethically responsible for a betrayal, which again, he is not.
Third: If he didnât betray his family, it must be Aslan he betrayed, right? Well, problem. Edmund canât betray Aslan. He doesnât know Alsan. He has no obligations to him. None of them do. Heâs a freign king, one who has, I will point out, abandoned his post and charges until very recently.Â
And at at least Edmund has the sense to question the one he landed with. The others get a bit of âChildren of Adamâ chosen-one ego stroking and sign up to be Aslanâs child soldiers based on the first thing theyâre told by the people they fall in with.Â
And while the âkid adventurers=child soldiersâ thing is usually a semi-ironic joke, Father Christmas pretty much says âHey kids, hereâs weapons cuz youâre soldiers now., so go stab some ho-ho-heratics!â before he hands them swords and bows.
Also, thereâs the lingering near-certainty that the entire set of events, including Edmundâs âbetrayalâ was engineered by Aslan, specifically so the Witch would activate his trap card and he could rid himself of the only other being with the kind of power that could threaten his absolute, magically enforced dictatorship and the rule of his groomed, foreign-born puppet royals.Â
TLDR: Mistakes are not moral failings, unlike this plot hole.