Suspension of disbelief makes it possible to read Harry Potter without disobeying God’s Word, regarding magic. You enter a fictional world where magic isn’t forbidden by God, but is a secret, academic subject, to be used for good or evil. I don’t believe it is inherently wrong to enter that fictional world, as long as you keep the magic there, as long as your Biblical worldview of reality isn’t altered because of it. Séances and witchcraft are not cool, fun, much less right, just because Harry Potter did it. Going through 1 Sam 28 would be a good orienting point for your older children who read Potter. I’ve only read the first book, and I did see some moral lessons and Gospel parallels in it. There’s plenty better stuff to read, but it won’t be forbidden to my children when they reach the right age (able to keep the magic in the fantasy world).
Some say we have no business imagining a world that contradicts the Bible. In response, I would agree it would be bad to delight in a storyline where homosexuality is a celebrated norm. The catch is that magic isn’t the same kind of problem, because magic is the perfect literary device to allude to unseen spiritual powers, over which Christ has triumphed.
So, it takes a suspension of disbelief. I say if we can’t do this, we disparage the gift of fiction, and we are missing a great deal of rich, Biblical truth to be found in stories like Narnia and Tolkien’s middle earth.