The situation is very important in this, as is the POV. If it's their own POV, I think 'man' and 'woman' is perfectly approriate. Depending upon their view of humans, you might even underscore it by refering to human males and females otherwise, like man='human', woman='humaness' or something along those lines.
In her "Foreigner" series, C.J.Cherryh takes this an interesting direction. The setting is an alien planet, and the physically human-like, mentally very different aliens are the dominant civilization, but a human civilization cut off from the rest of humanity and kept segregated from the aliens on an island they gave to the humans, interacts infrequently. The main character is one of the few humans that does this interaction. Thus the story is almost entirely within the alien society, but from a human POV.
She not only goes ahead and uses 'man' and 'woman' for both races, she goes so far, in recognition of the aliens being on their homeworld, as calling the planet 'earth' (lower case, for some reason), thus translating the alien word rather than giving it (most of the dialog is understood to be in the alien tongue.)
In essence, she's saying, in this case the humans are the aliens. It makes perfect sense in context. You just need to decide what makes sense in context with your story.
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Regards,
Eric Fretheim
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