I had 4 large Collies at one time. For a small trailer a Toyhauler can't be beat for floor space. If going with a large TT a large slide-out gives enough room (unless laying in the doorway) for getting around them.
When looking at TT try to imagine 4 dogs laying on the floor or take 4 dog beds when you look. Place them on the floor to give you an idea of the space it will require.
In 50 years of dog ownership I have never used a kennel. Just don't want to deal with the space they take up.