I've read all five books, seen both the movies, and plan on being at the theater tomorrow with my two neices (aged 6 and 4). Hopefully, God will not strike me dead for watching something about witchcreaft, and the girls won't attempt to cast an Unforgivable on me with their plactic wands. But if kids can watch Snow White, Sleeping Beauty, Beauty and the Beast, etc. (which all touch on witchcraft) without joining a coven, maybe the Harry Potter movies won't turn them to the dark side either.
God will indeed strike you dead, and your poor nieces, if I don't do it first, you demon-possessed monster, you. :)