If an organisation is that small, does it need to be an ATO? If its not offering commercial training, maybe a DTO would be more relevant. Normally, the HoT may be transient as the day to day operation is under the supervision of the CFI. If you are doubling as the CFI then that would suggest in your absence, that there would be no supervision. As an ATO you will have an approved Operations Manual, what does that say?