I've only camped in RV's (I've stayed in tents out there, but that's a different story...), and, except for one year we haven't had many problems.
The one year was with newbies who got so excited about the event they treated the RV like a dumping ground for their stuff. Floors, other peoples beds, by the door..... *aaargh* Somehow we're still friends.
Make expectations clear, and stick to them. Assign cabinets/ storage areas to people, and make sure they know to keep their stuff in them. If someone wants to cover their own bed with costumes that's fine, but don't plan on covering anyone else's with it.
Showers? For 6 people? In the RV? ........*oi*..... All that grey water to deal with, not fun.
If people must shower inside I'd limit to once during the week- water on for a minute or two, turn it off & lather up, another minute or two of water to rinse. Done. Best bet is to get a sun shower & evap pound for outside. Personally I bring No Rinse
shampoo & body wash. You just need a clean towel, no water at all. Give my face, hands & "bits" a daily wash & don't shower until I'm off playa.
I'd only recommend using the RV to sleep in- we leave the beds down at all times to discourage gathering inside. Build a shade structure & use that as your livingroom.
You'll have to base your specific house rules on your group- everyone's will vary. Dr. Pyro's suggestions are a good start.