in my opinion, as the tribe seems to behave as a unit and a family-type of structure, and, individually, they expect it of one another, I would baptise the entire tribe. All of us are baptized upon profession of faith, and, if this group profession represents their individual profession when done so as a whole, and they are used to their individual professions being decided as such, then I would honor it as an individual profession in the context of that structural unit.
Blessings!