When the weather cools off it is nice to move to some lower elevation camping opportunities.
Just two hours south of Boise is Banbury and Miracle Hot springs. Both have great camp spots with the Banbury being a little further from the highway and a little quieter. Banbury has more of kid focus and Miracle Hot Springs is focused more towards adults with private pools and deeper pools.
Near Miracle Hotsprings you will also find a lot of great destinations from massive water springs to pristine pools.
For something a little more unusual you can check out the Black Magic Canyon in Southern Idaho. This is a slot canyon with some amazing geology. Check out these two links for more info.
EASY DIRECTIONS: From Shoshone, ID, go north on Hwy 93 for 14 miles to "Ice Caves" (left) & "Bear Claw Trading Post" (right). Go 2 more miles north to turnoff (left) for Magic Reservoir west shore. Go about 200 meters and park in 12-space parking area on right. Kiosk describes Black Magic Canyon. Asphalt trail goes left from kiosk about 150 meters. At end of trail, continue about 100 meters to riverbed. Go left up riverbed about 200 meters to entrance into slot canyon fullof wondrous water-carved formations.
When leaving parking area, go back to Hwy 93 and go straight across and follow dirt road beside river bed east about 400 meters to "Old Hwy 93". Turn left and park next to bridge over Big Wood River canyon. Walk onto bridge and look both ways - another deep carved black gorge.
Campervans available for rent in Boise, ID and Salt Lake City, UT.