Read first, or watch first?
Your kid already knows the Disney versions, and that's not an obstacle; it's the fun. Read the original of a story they think they know and let them catch the differences themselves, because the gasp of 'that's not how it goes!' is the whole show. Start with a familiar tale for the comparison game, then wander into the fifty tales nobody ever filmed. Skim ahead if you have a sensitive listener; the content note is not kidding.