" found a loop that goes from Sixty Lakes Basin to Gardiner Basin, over Gardiner Pass to Charlotte Lake. It looks like it will take longer than the two nights I had planned..."
Just an FYI, as I'm not trying to talk you into doing the 60 Lakes-Gardiner Basin-Gardiner Pass-Charlotte Lake loop. Years ago, late 70's, I went into Gardiner Basin from Road's End in KCNP via Charlotte Creek and Gardiner Pass before heading over to 60 Lakes Basin, on my way further south to Wright Lakes Basin in the Upper Kern. There was no trail up Charlotte Creek at the time, and no trail until just below Gardiner Pass either. From there to 60 Lakes Basin, there was a faint use trail to follow if you paid attention, and even without it the navigation was pretty straightforward. It took me 3 leisurely days from Road's End to 60 Lakes Basin, and I was not travelling lightweight. My point is that 2 days would be perfectly adequate for a loop through the area, especially since so many people have been through there in the intervening 30 years, with the proviso that you are comfortable and competent with occasional off trail travel and interpreting maps if you happen to lose the use trails along the way. It is definitely a route worth doing, IMO, as it traverses some beautiful county. Best of luck, no matter which route you decide to do.