I would say the Hermitage for sure. Gaylord is neat to see the inside of, but the parking prices are awful, and when my parents won a weekend there last year, the rooms were funky!! The Hermitage is close enough to walk to the Sommet. You should be fine walking. If you want to see the Gaylord, go to Opry Mills Mall and park there and then walk across. It will save you the parking fee, and it is just across the parking lot.
We like to eat at Demos, and the Big River Grill. We went to a concert a month or so ago (NEW KIDS ON THE BLOCK!! WOO HOO) and parked behind the Sommet and walked to Big River to eat. Both are easy walks.
Hope this helps!