In all my experiences crossing at Rainbow Bridge in Niagara Falls both US and Canadian Customs have swiped/scanned my passport when driving across. I see the tourist buses pulled over to the side and the passengers exit into a building where I assume they go through a similiar procedure.

I have never been asked about any convictions, but they have asked if we have ever been arrested.

I think it is best you spend the money to consult a lawyer and be sure before you leave so you dont wreck your vacation and make your wife madder! Good luck.