We took both mother and father-in-law with us to the Keys for a week when they were about 80. We all got along great and had a wonderful time. That was 4 years ago and they still talk about it, as one of their best trips of a life time.
We had them sleep in the bedroom and my wife and I slept on the pull out. This not only gave them the best bed but it also allowed my wife and I to get up and start moving around as we wanted. Would have felt like a prisoner if it had been the other way around. We get up early, make the coffee and like going for a early morning walk.
They are really wonderful people and it made it easy. Don't think I would have tried it with my parents.