If the contents are totally written in different langanges, I would preferred to customise order info provider and shopping cart info provider to override template
CodeName in different langauages for notification.
(e.g. preset the email templates
Ecommerce.OrderNotificationToCustomer.FR_CA, according to current culture context or current user preferred culture, the custom provide override function handle to override the email notification template CodeName for your need.)
You can have different langauage versions of email template for your need.
But you should try using the Kentico suggestion at
Configuring e-commerce email notifications
Use customer's culture for emails: Specify if the system sends the customer emails in the shopping cart culture.