If you are travelling with children, you must carry legal identification for each child. Divorced parents who share custody of their children should carry copies of the legal custody documents.
Canada Customs and Immigration officers and United States Customs officers are members of or affiliated with Child Find Canada, Child Find of America, the National Center for Missing and Exploited Children and the International Centre for Missing and Exploited Children.
Be prepared to produce birth certificates. Anyone traveling with children not their own should be prepared to show written permission from the child's parent(s) and proper identification (birth certificate).