If you haven't been up there and aren't that familiar with the area, I definitely recommend beginning with the cabin loop. There are several water sources along the way making it easy to plan on appropriate backpacking stops.
Chevelon is a beautiful lake, but hiking in the canyon is treacherous, and it is noticeably warmer than the cabin loop area due to being nearly 1500 feet lower in elevation. The cabin loop doesn't offer fishing or the swimming options that the lake does, but you won't need them as much!
The Chevelon canyon hike (
http://hikearizona.com/decoder.php?ZTN=782) becomes treacherous the further south it gets and is largely exposed and sunny.
At the lake itself, there is a dispersed campground at the top of the road to the dam, and some flatter ground at the south (upstream) end of the lake (accessed via an easy trail at the end of FR180).
http://hikearizona.com/map.php?QX=1795Otherwise, the camping opportunities are best explored with a boat, which is a pain to get down there as there is no motorized access.
So go stick with the Cabin Loop.
