I like rotating captaincy at this age, but I would keep the meaning light.
If a child wants to lead the warm-up or say a few words, that can be a nice experience. What I would avoid is creating the idea that captain is a special status awarded to the most confident or “best” child.
Different children can lead in different ways. One might speak in the huddle. Another might help collect the team. Another might be brilliant at encouraging someone who is nervous.
So yes, offer responsibility, but do not make every captain perform leadership publicly.
The armband can be a fun way of showing that everybody gets a turn to contribute.
If captaincy starts creating anxiety, competition or disappointment over who has it, I would simplify it immediately. At U8 the aim is belonging and small responsibilities, not reproducing an adult first-team hierarchy.
