Be careful with a Release of Liability or Waiver , it actually constitutes an organized or sponsored ride and is usually not worth the paper it's written on . Make it known with several "ears", that it's just a group of friends on a ride .
Sorta like a "Beware of the Dog " sign , it just proves you have prior knowledge of a potential liability .
You call it "Ride for Toad's Rights" or whatever , and some dweeb crashes everyone and lawyers up , it could get ugly .