Legal name changes

As Lisa said all paperwork is the responsibility of the couple, the officiant just checks all the legal bits and mails it out. But they may be able to at least know what you need to do in your province and might be able to offer some guidance.

Very cool that you are both taking a new last name together! I always loved the idea but FH is dead against it

Hi Emma! That's a cute name! Definitely matches your mermaid theme You should take a look at this article to see how you can change your last name after the wedding. How to Legally Change your Name

However, I think you should also check with government procedures to see if the process would be different since the last name you want is not one of your current last names. How did you come up with the name? Are you a fan of mythology?

Normally those are not responsibilities of the officiant. There's a variety of documents like long form birth certificate etc that needs to be provided to I believe the federal government when you are changing your name legally and possibly provincial in the province of British Columbia, I'm not entirely sure as I'm more familiar with how it works in Ontario. That being said, you could ask your officiant if that's a service they provide, normally it's not. If they do decide to help you with it they may charge you a fee.