Well my mum (huge star wars geek, has seen all of them in cinemas) showed me them IV, V, VI, I, II, III and obviously now VII. I would let them watch the prequels, as although I despise them now, I enjoyed them as a child, but definitely after Vader tells Luke he is his father (SPOILER) or even Luke telling Leia they're siblings. But no matter what start with IV and end with VII
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