We love Gamestop. I order games online and purchase in the store all of the time. They sell used and new games, all come with a warranty. If you get a used game that has issues, they readily exchange it for you - no questions asked.
I Googled it and it looks like Gamestop does do business in Canada as well as, the U.S.
Now, as far as games for a 3 year old, sorry I am clueless. My youngest is 16. But, I Googed this and a few suggestions were Carnival Games, Looney Tunes, Alvin and the Chipmunks, Disney Cars, Lego Indiana Jones, and Mario Cart comes highly recommended from several resources.
Hope this helps a little! Enjoy your Wii!!!