Formal:
* Delegation: This is a good choice if the representatives are working together on a specific task or mission.
* Embassy: If the representatives are diplomats representing a country.
* Assembly: This emphasizes the gathering of representatives for a specific purpose.
Informal:
* Group: This is a simple and straightforward option.
* Team: This suggests the representatives are working together towards a common goal.
* Body: This is more general and implies a collective unit.
You could also use a descriptive phrase, like "a body of representatives" or "a group of elected officials."
Ultimately, the best collective noun depends on the specific context and the tone you want to convey.