Long story short: Mr. S’s grandfather disappeared in 1926, and no one knew what happened to him until this June, when we connected with the progeny from his second marriage. We didn’t know he had a second family, and they didn’t know he had a first family. They all live in Canada. Grandpa died in 1964, but there is one youngest surviving son from each marriage (ages 70 and 75). So one weekend in September, we’re going to drive Uncle LeRoy up into Canada to meet his half-brother for the first time, followed by a big “reunion” of family members who’ve never met. 
Here’s the General Question: What exactly, in practicality, will we need to cross the border at International Falls? I’ve checked several “official” sites, and it seems they either give contradictory information or require a flow chart to decipher. So I turn to those who have actually crossed the border, and I’m sure there are one or two of you around. Do we need to blow the $12 each on a certified birth certificate? Is that enough, or do we need a second form of ID? What’s the Straight Dope?