On the "far" end of P2 there is indeed a part reserved for mobile homes. We've stayed there for the last 5+ years. As already stated you can easily walk to halls or take the bus. There are toilets and showers.
In the first years I made a reservation beforehand, but the last few years I didn't bother any more. We usually arrive on Wednesday and they never had our reservation on the list. We now just show up and enjoy the Spiel!
Thanks for the info! My wife and I were thinking of camping there, but we weren't sure if there were toilets and showers. We'll be camping in the back of a small van (Renault Kangoo) instead of a mobile home, do you think that will be an issue? Also, do people play games during the evenings at the site?