The first piece of equipment you should have after buying a RV is a tent. Put it under the dinette or bed in storage and when someone asks if they can come camping with you, say "Sure, I've even got a spare tent if you need it." Then you can go into your statement of how really crowded the inside of the camper gets when it's more than just your family but how you love having others camping in adjoining campsites and sharing the fire at night.
Laying out the ground rules in front is critical to not having a bad time or ruining relationships and friendships.