We took our nephew with us 2 years ago to dinsey. We did get a note signed from both parents advising that they gave us permision to take their son across the border with us and that if anything medically was to happen to him while he was in our care we had the right to give permission for medical treatment. We never got it notorized. When we crossed the at the border in Windsor, we showed all our id. The person never asked for the note even though our last names were different. We actually never had to show the note during the 14 days we were in the US.