My estimation is that Canadian spelling is 50% American, 40% British and 10% uniquely Candian (words such as 'dietitian' which both Americans & British spell, 'dietician').
As an Australian (Australia has some unique vocabulary rather than unique spelling), I would choose either American or British spelling and use it consistently throughout the book.

Actually, I'd probably use American spelling, which certainly seems to be more common in Asia. And despite having been schooled based on British spelling, meter makes more sense to me than metre, personalize makes more sense than personalise, plow is better than plough, color is better than colour and so on.
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What about ass or arse? If somebody kicks your ass, would you call the police, the RSPCA, or both? No, too much gets lost in in any oxymoron English. I t would take us a week to discuss why. I am happy in China that many Americans are starting to say Autumn instead of The fall. Where do you go to if you want to say Autumnal? Bit clumsy to say fall-like. What about spring? Shall we ignore it's own adjective and say spring-like? We could be referring to those things in beds. COLOR is bloody awful, it looks awful. I notice if the Chinese want to use colour in an advert, they usually put colour or COLOURFUL as opposed to COLORFUL which really doesn't do anything for you visually. Grammar and "American" English is a disaster area. We must not forget "American" English came about as a political decision, not to improve English, which it certainly does not.