DH and I were there in April, but we did White Rim trail tour in Canyonlands, so I can't really help you with the trails.

We found the dining in Moab to be a little frustrating. It was packed in April, so it was hard to get into some places without reservations. We ate Italian at Pasta Jay's a couple of times. That was good, if a little loud. We got a lot of our food at local grocery store. They had a pretty good deli so that was our default. Miguel's Baja Grill is supposed to be good, but it was always so ridiculously packed, that we never got in. I don't know how crowded August is versus April, so perhaps you'll not have as many problems. I think the town clears out a bit during the heat of the summer.

Have fun! As someone from a mostly flat midwestern state with a relatively inactive populace, Moab was like nothing I'd ever seen. Bike, bikes and more bikes.