Q:

One word for witches and wizards

Is there a single word for witches and wizards both, regardless of gender? 
Edit 1: Is there a single word for the category of people who do magic (like witches, wizards, warlocks, sorcerers, etc.)?  
Edit 2: The usage example comes from a story I made up for my niece.  She wanted to know why I was designating male cats who do magic as witches alongside the female cats.  Shouldn't they be called wizards, she asked.  I then wondered whether there's one word that encompasses everyone who does magic. 

A:

Your edit includes what would have been my first choice (sorcerer) (but then again sorceress does exist, as mentioned elsewhere). 
With all that in mind, I'll suggest conjurer/or:
"a person who conjures  spirits or practices magic; magician"
(Dictionary reference)

A:

I would suggest using either Mage or Magus (plural: Mages and Magi respectively).  Both of them convey a gender-neutral magic-user, without giving off a sense of being a mere illusionist. 

However, the term "mage" has fallen out of use, with wizard and witch
  being the standard terms for any magic user.  The term "mage" is gender
  neutral. 

I'd consider Mage the more neutral option of the two, as Magus has a slight hint of masculinity from Latin.