If you were to retake and use the American DAT, you'd have to prepare for the QR and Orgo sections that aren't on the Canadian DAT (on the plus side, you wouldn't have to worry about the soap carving section). I'd personally stick to retaking the Canadian DAT if that's what you're most comfortable with.
I don't think retaking is absolutely necessary - most schools friendly to Canadian applicants will accept the Canadian DAT, and your scores are fine (I suspect they'll just discard the MDT section score since there is no american DAT equivalent for it). But I personally would - getting in as an international applicant is generally more competitive, and a higher DAT will help improve your prospects and make up for the lower GPA.