A buddy from work went (tried actually) on a fishing trip several years ago to Canada and his brother got turned away at the border because of a DUI. Don't know all the circumstances but sounded like he looked into it and I believe there was some type of process to get a 'pardon', waiver or whatever they call it in Canada - but had to be X number of years ago etc etc - sounded like a hassle to him so he just dropped it. Now if they go on a fishing trip with his brother that has the DUI they pick a destination state side.
I would certainly check into it before you get to far into planning for the trip...
http://www.tripadvisor.com/Travel-g1...nvictions.html
"Thinking about traveling to Canada? You'd better reconsider if you have been convicted of DWI or DUI (Driving While Impaired or Driving Under the Influence) within the last
ten years. Any type of impaired driving offence is considered the equivalent to the Canadian Criminal Code offence of impaired driving. This includes misdemeanor convictions. Canadian law considers impaired driving to be a serious offence... "