No worries; I didn't take your comment to mean that.

I do like your suggestion of using "they both" and "they all" for disambiguation.

I learned German as a child and Spanish in school, so the 'familiarity' protocol is somewhat familiar to me (hehehe). I was sometimes corrected on which to use when back then. I might have used "Sie" speaking to people like my aunt, thinking it was how one spoke respectfully to an older person (or not thinking about it at all), when really I should have been using "Du". I'm still not sure I always get it right, and from what I've heard the usage has changed a lot over recent decades anyway.