Not from Canada - but I have done the shipping stuff from Disney home waay to many times, and this may help.
There are two shipping centers on property - one at the Contemporary over at the business center - and the other at the Coronado - again at the business center. We use the Contemporary - when you come in go to the right - through the doors into the business center - if no one is at the desk, go to the right, down the hall past the escalators and there is a little office (just past the bathrooms) there should be someone there. If you really have a lot of stuff, pull up to the valet and let them know you need to take alot of stuff to the business center and ask to double park - they should direct you to pull up about 30 feet. They can ship usps and fedex. If you are on property you can have it charged to your room too.
I haven't tried this next method, but I've heard it from more than a few folks in the shops.. when you are in one ask about it. Buy your stuff all over property - keep all your receipts. Take all your items and your receipts to a shop, and they will ship everything home for you at Disney's rates.. so instead of paying to ship things home at the register for each transaction, you can have Disney do it all at once. I've never tried it though.. Usually one benefit to shipping the item right from the shop, atleast for those of us in the states, is that Disney waves the taxes. Which can sometimes be more than the shipping!
Good luck..
--heather