I think it’s a good idea to use Discourse for reaching project week participants but I think we should simply create a new topic (Project Week #25 announcements) or maybe category (Project weeks) that participants should subscribe to, instead of using groups. Problems with groups: messages are not public, so people who join the group later will not see previous announcements; not obvious how to send messages (you need to use the “message” feature and enter the group name); groups and messaging are new concepts that users would need to learn.
Since the group is only a convenience to allow sending a message to all attendees, creating a topic Project Week #25 announcements make more sense. See Project Week #25 announcements