As long as you don't buy World Adventures (which needs to match region codes), you should be able to match the japanese version with the Canadian base game. I'm unsure about the language cause I don't know if they contain the english strings (especially if you buy the download version).
Normally, the EPs just follow the language of the base game (that's how it is for me), the installation process is usually in the language you bought the game in but the language ingame should be the same as the base game, as long as the english strings are availble.
That's how it works for the DVD versions. I'm not so sure about the download one. From what I saw, you choose the country on installation and not the language but I don't know if what happens if you choose a different country then your own, if it's in the correct language then or not.
To be on the save side, I would contact customer support
They can be found here: https://help.ea.com/contact-us
Choose a category, a game and a platform for the contact options to show up.
If live chat is gray, change your country to US and make sure you're on US Business hours. It might also gray because they're very busy. Try later.
See this post if you have trouble with the site: http://sims3.crinrict.com/en/2012/10/how-to-contact-ea.html
Beware that there's no longer an Email option
