What camper to tow with 1/2 ton and decent MPG

My advice, 6800lbs isn't going to get you a huge rv anyway. Give yourself a 10% cushion at least, then go look at some units in your weight and price range to get an idea what you are looking at. A decent sized pop up will give you the best mileage and easiest towing experience, and can handle 2 adults, 3 kids. Buy a decent used one, take care of it for a few years, then upgrade when the time comes. That is also a good time to upgrade the truck;)