I read about such things as a child. I do not remember ever believing that spells were real. I do remember wishing that they were! I also wished I could fly like Superman, etc. I say this not to mock; as a little boy I often had fleeting wishes like that. None of them lasted past the time I closed the book.
The bible warns against witchcraft,on that basis I would not take my grandkids to see the movie nor would I buy the books....
This is America,even practicing Wiccas have a right to be here and worship as they choose..But I do think Christian parents need to think about the choices they make for their kids.