We were only English speaking at home, though DH did remember quite a bit of Spanish. I grew up in Canada and used to speak French but consider it a soon dead language.

DD started Chinese at Sat school in K. Asian languages tend to be hearing based and starting early is good and she learned the Taiwanese way, with bopomofo symbols. And did Spanish in school.

I would base in English but use a good tutor for Japanese. You want them to hear the language.

But I know little.
Ren