Don't forget to add the weight of passengers, water, fuel, and ALL gear. You will need HD cooling and suspension system AND trailer brakes. Did you ever see the Airstream promo picture of the guy pulling an Airstream with a bike? Pulling and pulling safely are two different things. One of these days, you will want to pull into fast traffic or go up a hill, or have to make a quick stop.
RV dealers have a bad habit of telling big fat lies about your towing ability.
Don't endanger your family. If you need passenger space and a big chassis-get a used 1 ton passenger van.