Regarding Lodgepole, actually, swimming can be accompliished in the river there (it is pretty shallow come August, but its great for the kids) and I have never had too much trouble getting some late camping reservations there...much less crowded or busy than Yosemite before I wrote it off, I'd give it a try. Crystal cave is nearby, as are nice small-summit day hikes like the Baldies, and the walk up to Tokopah Falls is gorgeous.
Having said that, King's Canyon is also sweet and well worth your time. I am not sure if there are great places in the canyon to swim, but there may be some. It will be *warm* there!
Wilderness forever,
Bruce Jensen