The kanji 達 as a suffix is used to make explicit a plurality, like in 私/私たち and 子供/子供達. Also is used with person's name to indicate he/she and his/her group, like in ヒナ達 Hina and her group, サトシ達 Satoshi and his group. So my question is: what is the parameters with which I choose a certain name or another to attach to 達? Why should I use ヒナ, and not サトシ to indicate the same group?
One reason is, of course, that I don't know the other person's name, but what else?
Linguistically, you are free to pick any of the members when calling the group in the format of name-たち. It depends on which person you want to highlight for whatever reason. It's not like some names are grammatically compatible with たち and others aren't.
I would probably choose the name of a person both I and the listener know, because, well, otherwise they will be confused. I'm sure this is not specific to the Japanese language.
That said, if you, A and B form a three-person group, it will be weird for you to call the group Aたち or Bたち, instead of 私たち (and for me to call Aたち or Bたち, instead of あなたたち or its variations). There is a sense that name-たち is a third party and doesn't include "you" and "me".
