Staying at Wawona was a great way to see Yosemite. It's not too far from the Valley but a lot more peaceful. We got lucky and were able to snag a spot without a reservation but I would recommend getting a reservation if you can because it's very popular.
My family has been camping here since before I was born and we love it! It's definitely a gem of the Sierras. The lake is beautiful and Sand Pond is great for swimming. There is plenty of hiking and fishing around and it is such a peaceful place to relax and read a book. I would recommend hiking up to the Buttes if you're looking for a challenge. Be sure to stop at Bassett's for some icecream on your way out!
Washburn is the primitive campground behind San Simeon Creek Campground. You can save some money and stay here if you don't need hook-ups. It is great and has fairly level sites with plenty of tent space. There are a lot of birds/squirrels so make sure not to leave food out.
This is a great campground close to San Luis Obispo. It is great for tent or RV camping and is located near a park, garden, and golf course. It is a short drive to San Luis Obispo or Morro Bay where you can hike, shop, relax on the beach, and eat great food.