We'd maybe look at a commercial side but to be honest I'd be happy just letting mates come round ride, bbq and get drunk. In whichever order suited the ambulance availability at the time!!
On the thread mentioned in my previous reply, there are a couple of videos (slide shows technically!) of just that sort of thing. It was done for several years, on a 1/10 mile "practice track" cut into a mate's backyard. He did exactly as you are - chose this house because it had space for a track. Anyway, it was much fun. In fact we even named it "The ______ International Raceway," as there was one guy who came down from Canada!
If you saw the dirt track at Willow Springs, it's a cushion! Here's one of my favorite clips from there.