Not so hard to arrange. Have run private WW2 battles before. Yes you need suitable place, PLI, H&S Risk Assessment, notify Police, sort out wrist bands, rules, timetable, toilets (if you want a Shower - get a B&B). Ensure book in advance - no on the day entries etc... ideally walking distance to a good pub with great food and an accommodating landlord. Possibly even a small website.
The above can be managed by a very small (last time I did one, there were two of us to set it all up and run it) - unless you are planning a cast of thousands.
It all changes though once you move away from Private members only event to inviting members of the public.
Tim