What a great question! Perhaps I can answer it with some questions, just like Jesus often did.
Which is greater and more 'dangerous', the Spirit of God in you or any spirit in the wiccan?
If you and your kids know the Truth can a lie overcome The Truth?
Is your experience of God real (like the wiccan's may be of the 'spirit world') or are you 'playing church'?
Did any believer in the new testament ever have a problem that they couldn't handle involving an evil spirit or someone involved in paganism?
Whom are we told to fear, God or satan?