Just look at your job as anyone else who is not a sysadmin would look at his job. I mean: what is your goal? Then answer:
Did you reach your goal? If yes/no; what's your progress?
What are your next goals? Do you have the manpower, being on your own? How long will it take? How's the planning going along?
How is the system doing on a technical level? Is it fast enough? Room for improvements? Is the security up to par with todays threats? And how do you keep up with the latest IT developments and security threads?
How is the system doing for personel? Is everybody satisfied? Room for improvements there? Etc.
Is the system 100% fit for its purpose? Is it still functioning well enough? Do you need hardware upgrades? Etc.
Awnser these questions in a nice format. Google a status report format that is NOT an IT status report and use that one. Finally give it to the person. Just ask him if he wants a monthly or quarterly status report.
That should get you going.
PS: Do not report on anything too technical like "Our BLT drive just went AWOL" and you should be fine ;)