I am a quite fanatic bicyclist (and I use my bike also for transportation, as in bike holidays, covering 100 km stretches in one day, carrying tent and camping equipment.)
Try to build up your endurance the coming two months... If you can easily do 50 or 60 mile rides in early September you are on track. Take it easy the week before the big ride.
Drink enough, also in your training rides. Fill up those drinking bottles, for me, water works best, "sport drinks" tend to be too sugary. Eat regularly during the ride: sweet bread/pastry like things work great and can be eaten without getting off the bike. If you feel a craving for something specific, your body is often right.