Bernie - With only one of the six having prior Whitney summit experience, that means that five have never tackled the 97 switchbacks before. Also not knowing if your group has any high altitude (13,000+ feet) experience or not, makes it hard to give a good starting time from Trail Camp. My recommendation is to start as early as possible, but probably no later than 7:00am. You'll have five miles from Trail Camp to the summit, and that should give you the needed time to start your descent before any thunderstorms might appear (they usually show up in the afternoon). Good luck.
Michael T.