If you are looking for a campground or other hotel in the area for the reunion, you can simply look for hotels and/or campgrounds near Opryland. I would not stay anywhere more than about 20 miles from the host hotel which is right next door to Opryland if you plan on being at the reunion every day. We live 23 miles from Opryland in Gallatin and it takes about 25 minutes to get there with Nashville traffic. It will be much easier on you if you stay in the North or East side of Nashville. You don't want to have to drive across Nashville any time of the day.
There are 3 campsites within a couple miles of Opryland.
There are also 3 places relatively close
Elm Hill - 10 Mi
Seven Points - 15 Mi
Cages Bend - 22 Mi
There are a number of other hotels near Opryland at various prices. Make sure you stay within about a 15 mile radius as you look. Briley Parkway is the main access to the Opryland area. So if you stay on the east to northeast side of Nashville you will be ok. I would not go any further than Hendersonville to the North.
There are too many to list, but there is a group near Opryland and there is a group near the Nashville Airport. If you stay in those two areas, you will be close enough to the Inn at Opryland to get there easily.