actually, all you need is a few CR5's to spam it a bit a week before the race, hold it at prime time.
basic things you need:
1)locked continent
2)a rather straight route without too many water ways and cliffs
3)a specific veichle. otherwise the ATV will own all. on the last day of beta there was an ANT race on emerald for example. I wouldn't use tanks and such, not really fun to drive and if they start shooting each other the race is over
4)lots of reavers and mossies flying around, they'll see the leaders and all, make sure nobody spawns and gets an ANT near the finish line.
5)a CR5 running the show.
what I would do is tell everyone to get in their cars in the CY of some tech plant, to make it easy to get reavers. give the go by firing an orbital strike and have a friend set one up at the finish line. first person in the beam is the winner and gets his head blown off as a reward