The Agenda for a General Meeting, including a Proxy Form and all prescribed inclusions, has to be served on each Owner a minimum 7 days prior to the date of the Meeting, and as there’s no mention of calendar days or business days in the Act, you need to receive that Agenda by this Thursday in order to then hold a valid Meeting.
Regarding your proposal to change Strata Managers (SM), ensure that the Proxy Form includes the specific paragraph on this matter (para 3), and that you read the Agency Agreement carefully, as it customary for a minimum three (3) months written notice to be given to the SM in those circumstances.