Here some more vids of how it is done in other area's
This one shows a US rider doing well in the New Zealand open championship. It looks like they are running this race on a go-kart track or something like a inline skates track.
http://www.youtube.com/watch?v=nxZ5cP545TkTowards the end you'll see some close racing between 5 blokarts.
Following the link at the end of the clip brings you here :
http://www.classactionracing.com/And it looks like a piece of US seashore promenade that has been converted into a blokart track.
Here more of same NZ event :
http://www.youtube.com/watch?v=DWoth4vbQy0In the UK I hear they often use abandonned WW2 airstrips. Lots of those around there.
Here in NL we have plenty of beaches. I never knew blokarting has gotten so big here in NL, in this video there most be about 50 landyachts on a single start :
http://www.youtube.com/watch?v=5BvEE3TkDhYMary if there are relatively large spaces between the little green islands then they may not be to much of an obstacle hell you can use them as markers.
In other area's they just ask the local county to use a piece of backroad (that is sufficiently wide).
Here some USA desert karting.
http://www.youtube.com/watch?v=qnUB9ZeTpaM&mode=related&search=Wouter