agree with Steve about using Diamox. Your schedule STARTS above 8,000 ft, the very official medical definition of high altitude. People get AMS at "only" 8,000 ft, they do not need to go to Mt Everest. In a group your size, at least one person is statistically likely to have AMS symptoms to some degree.
I've been to the area many, many times. Lowest August temp I have had at 12,000 camps has been 18F. While 30 is more typical, I use a 20 F bag and glad to have it. In the event of illness, injury, or wet you want more bag, not less.
