Children can distinguish between fantasy and reality, between false myths and the True Myth, the Great Story of which all other stories are but pale reflections.
Is science fiction also on your 'road to hell' list? Should I read nothing but history and biographies? I can't help thinking that God made us in such a way that, for some of us, fantastic stories touch a note deep within us - what Lewis was talking about in 'Surprised by Joy'.
Your relationship with other created beings, especially if one condones the invitation of sorcery or encroachment of spiritual beings outside man's domain,...into our domain,...becomes the affronted affairs of fellow men.
By no means should we ever condone sorcery or witchcraft. Place our faith instead upon Him through the Lord, Christ Jesus.
The HP issue involves the introduction of the spiritual domain to children in a fashion which fails to worship God, but encourages a worship of the occult.
BTW, what's your Scriptural basis for worshipping Fantasy?