I am posting this for the benefit of people who are planning to travel in an RV at some time in the future and are lurking on this website to gather information, as I did before I retired and started ...
We have never traveled on our RT without our dog. We try to RV only in the spring or fall, so heat has not been a problem. At one point we had two dogs (a lab and a sheltie) a cat, and a goldfish with us - we and they all enjoyed ourselves and got along fine!