It is hard to justify calling a meeting. Do all five of these people need to be here for the next hour? Are we brainstorming? Is something unclear?
Brainstorming during a meeting is not always a good use of time.
When is the last time that, when called upon, you were able to summon all of your creative energies to focus into a burst of inspiration about something, anything? Can you do it in the next 10 minutes? Hour? Or in a room with all these other people, at the same time? In the ideal situation this would be a difficult task, in reality, Mary didn't get her coffee yet and...