As far as space goes, I think it depends upon the size of the camper.My camper has plenty of space for two medium sized dogs.
one dog would have the rear couch all to its self, and there is plenty of room for another dog on the U shaped dinete couch with room left over for two adults.There is also plenty of room in the rear slide for a dog on the floor between the rear couch and the dinete couch.
The floor is wide enough so that you would not have to step over the dogs and still have full access to everything in the camper.
The camper getting hot would always be a concern, how much depends upon what part of the country you are in.