If I understand correctly, my answer here is what you’re looking for. You’d use the Assign Duplicate Tasks feature for your team (if you have an Asana team corresponding to the attendees, or create one, or just type all their names into the one multi-person entry box). You can do this as a subtask, if you already have a task representing the meeting itself, and then the multiple tasks will both be subtasks here and in everyone’s My Tasks: