I don't know about a demolition derby for minivans. One of my friends participates in demolition derbies. Seems to have a lot of fun with it. Right now he's got an old Suburban waiting for an appropriate derby to participate in. I think that would be better than a minivan derby: A full size SUV derby.
But the real derby I want to see: I think they call it a combine demolition derby. If you don't know, combines are one term for those big farm implements that harvest grain/corn/etc. (Frank from the movie Cars).