Your child's nanny should definitely be travelling with a notarised consent to travel letter, showing she has consent to travel with your child. Also, be sure to include your contact information on that letter. Along with the letter, it won't hurt to send along a copy of the biodata pages from both parents' passports. I would recommend you schedule it so that you're at the airport to pick them up if possible.

A sample letter can be found here:

http://www.voyage.gc.ca/preparation_...tement-eng.asp