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.