I don't see any obstacles blocking you from entry as a non-traditional student. Our class's average age this year is 23 years, however, some 25 students out of 120 are age 25 and older. I think is reflective of the smaller number of older applicants applying, rather than any sort of discrimination against older applicants. By and large, the older students bring another dimension to the class, often having experiences that the younger students lack.
However, your lack of Canadian citizenship is a huge obstacle. UBC currently does not accept any applicants who don't hold Canadian citizenship. You might want to check the UBC website which is located at www.med.ubc.ca As far as I know, only McGill university and Memorial university accept American students, and these universities are in Quebec and Newfoundland respectively. You might want to check out Sean Winter's page, as he has links to all 16 Canadian medical schools. You can find his site as the first entry of my Links page.