I am going to be driving across the border from Seattle to Canada in August with my grand children ages 13 and 15. Their parents will not be with us and the children's passports expire in January. Will we have any problems crossing the border?
Canada requires passports to be valid for the duration of a visitor's stay. There is no requirement for additional validity.
You could bring a notarized letter from the children's parents permitting you to travel with them. It's unlikely to be necessary, but if anyone does decide that something untoward is going on, the letter should help dispel their suspicions.