Lenses for Motocross video?

[brok3nsalvation]

I have a Canon T2i with just the 18-55mm kit lens, and also a 50mm prime I was given. I'm a beginner film maker, and plan on shooting a video for my step-brother this summer of motocross. I want the style to be similar to Moto: The Movie series, Kickstart or Epic (all motocross films), kind of a documentary/stylized look at the sport. I noticed most shots have a very deep depth of field, where as everything is in focus. How do I easily pull this off, and what lens would you recommend for doing such a film?

Again, I'm a beginner, so sorry if this is a stupid question.

I appreciate any response.
Thanks!