Are Khala's pets somehow immune to his gaze attacks? The description states they effect "any creature within 30 feet..."
Khala's pets are basically roadkill at the levels the PCs have achieved by that point. I say go ahead and let them be afflicted by Khala's gaze; it plays up Khala's ruthlessness, and the Skulvyns are really only there as additional squishies anyway.
i'd say they are specially trained blind skulvyns with blindsight or something
Skulvyn aura is Will Dc19 to avoid, Khala is +20. Even if Khala fails, he's slowed 4 rounds and then gets another save. Once you save, you are good for the day.
So by the time the PCs arrive, Khala has already made a save.
I've gone under the assumption that with creatures that are often (supposedly) in the company of one another for a great deal of time, especially those operating in concert with one another, that their auras/gaze attacks are ineffective on one another. Whether you feel that this is fair as a DM or not is up to you, but I feel it's completely appropriate, and remains in the spirit of the encounter.
Oh look a nat 20 *accidentally bumps dice when moving the DM screen*
I actually figured they make the save sometime before tea, so when they meet the PCs at lunch... *shrug*