I think my gearing is okay, I am currently running a 42x16 or about 70 gear inches and do well on hills. I may look into the White industries double freewheel though since this is new territory for me. It is probable that it will be windy, it seems like there is always at least a 10-20 mph wind here some times more, rarely less.
I think my riding partner will be good at keeping me from going to fast to early. He is the sensible one, rarely does he suffer from over exuberance the way I tend to.
As far as food goes, should I use Clif bars and jerky or do you have better recommendations? How often should I drink Gatorade? It will likely be at least 90 degrees. On my normal rides I use just water but, I know I will need to replace electrolytes for such a long ride in the heat.