I agree with Jane.
Small steps first before we start trying to run. Try a poll asking people if they would attend a track day in the week or at the weekend only. Find the numbers and then look at potential book-a-track track or similar track days. Nominate one, then everyone who is interested books their slot.
If this works a couple of times and numbers are high enough, then we consider other stuff afterwards.
We can't sell 20 slots at Japfest so I don't see how we've got a chance at anything else with more than 10 attendees.