I used to go to Moab for 4th of July's. Always very hot but I was always out at dawn and back in to town early. The town is kind of nice as are the trails as there aren't many people around in midsummer so you can quietly enjoy the town, trails, etc without running into a lot of people. I would recommend going into the La Sal mountains. Do Geyser and La Sal passes. Not hard at all but up high and there are great views in all directions. Great places to camp as well that are much cooler than the desert. There are a number of other roads, trails all around the peaks that mostly are easy but very scenic and a lot cooler than the lowland desert. Some lakes as well that the kids would enjoy. Other than the La Sals----Out at dawn and you can run anything but the heat comes on very quickly.