i'll give it a shot, here's some stuff off the top that might sound "cool" to an 8 year old
Tokyo Speedsters, Fusion Express, Metro Speed Dynasty, VeloCity Inc.(import/fast&furious)
Muscle Car Maniacs, Wanted Vigilantes, Bounty Hunterz, Roadster Outlaws (mad max style)
Interstellar Entity, Galactic Horde, Starswarm Fleet, Cosmic Battallion (alien futuristic)
that's all i can think of