As already mentioned, you should have no problem with Mammoth Campground. There are some longer pull thru sites at Pebble Creek, if you can find one open. No generators allowed at Pebble Creek and IIRC the water is from a hand pumped well.
The Lamar Valley is worth the time to get there as in our experience the largest Bison herd is there. While somewhat a matter of luck and timing, we have on several occasions seen wolves and bears there. A few miles beyond Pebble Creek toward the Northeast Entrance is Baronnette Peak, with Mountain Goats high up on the cliffs usually visible with binoculars. We have also seen Mountain Goats on the mountain side across from the Pebble Creek Campground.