You can be anything you want!
Personally, I think saying your a 'Christian Wiccan' is very contradictive.. its like saying you're a 'Hindu Muslim'. But of course, you dont have to be Wiccan to practice magic, 'Christian Wiccan' is just a phrase I hear a lot.
So yes, you can practice magic, as magic itself is not a religion, but rather a practice.
(Although you can get 'Christian Wiccans.)