Since this sounds like a work trip, I would find a replacement and not even risk it. Its one thing if you're heading up for personal reasons and get turned back. It's another if it's for work and you get denied. I've personally witnessed guys I work with stuck in secondary for an hour or more because they put down "work" as their reason for visiting, and the Canucks go nuts. I had a guy who had to spend the night in an airport hotel, under threat of 'if you leave we'll deport you" because Canadian immigration couldn't decide if he needed a student visa or not. He didn't, but because he put down "attending a class" for his 3-day seminar on routing IPV6 via MPLS instead of just writing "customer meetings" or something, he got delayed an evening and most of a morning because of it.

Canada can be a pain for your average business visitor, much less one with a very recent DUI conviction. I wouldn't even chance it, both for yourself and for your company. Find someone else to handle this visit.