Glad ya'll got a place to ride, I like that a random dirt bike passed by. One thing that really surprised me with all the rocks, dirt, dirt, etc, ya'll have no goggles or glasses, or eye protection at all. This isn't an old man saying this, I'm a 24 year old frat boy... losing an eye is not cool at all... wear something, even if its just some sweet aviators.
Okay, this seems impracticable and super dangerous, but have you considered you having someone sit on something like a trailer being pulled by the kart, I bet that would be an insane ride, very dangerous, but could be fun. I'm not saying by any means you should do this given how likely you'll get hurt, but have you thought about that before?