I have always taken a simple consent letter written and signed by my wife stating that we are married and that she grants permission for [name of child] to travel with me to Canada on [start date to end date].
Include your wife’s name, address, and phone number where she can be reached.
IMPORTANT. In the unlikely but certainly possible scenario where a border agent would try to call your wife to verify something, it is critical that she actually answer the phone.
If your wife is anything like mine, she will be multi-tasking on Facebook and Pinterest when the border agent calls and then decide not to actually answer the phone because it’s an unknown number. She will then start texting with her bestie and ignore the second and third call as well. Make sure your wife knows when you are about to cross the border and understands she needs to actually answer any and all phone calls during this timeframe. I call my wife 20 minutes before we cross the border so she knows this is the one time this year where she needs to actually answer her phone.
There is no requirement that I have ever seen that this letter be notarized and I have never done so.
Grouse