I am confident that JT would be correct about conduct of SC meetings in NSW. However, why do you ask the question? If a decision on a matter is finely balanced, it would be poor form for a subset of committee members to hold a meeting and decide one way when some members were unable to attend and they had made it known that their view was the other way. Even if legal requirements were observed for proper notice of the meeting and there was sufficient attendance for a quorum, the decision would be liable to being reversed next time the full membership of the committee could meet. If the decision had been acted on and could not be reversed, it would sour relationships.
On the other hand, if the purpose of the meeting was to decide an uncontroversial matter in which all were agreed, I think you could just discuss by email or other means to make the decision ‘out of session’ and record the result in the minutes of the next formal meeting.