your Secretary is responsible for scheduling additional special Governance Meetings promptly upon request of any Core Circle Member. So your Secretary might had the option to schedule one right after your Tactical Meeting.
I would not combine both into one but - what helped in one of my cases - is to have a Governance Meeting following a (weekly) Tactical Meeting every second to fourth week. You might want to consider the frequency based on your needs.
I would not mix the Tactical & Governance into one especially at the first steps of Holacracy Adoption. You might want to consider Shu - Ha - Ri (https://en.m.wikipedia.org/wiki/Shuhari).