Just a few suggestions. Make all rides start and finish at the same place. Point to point rides are logistically tough. Keep the century ride reasonable, a nice mix of flats, rollers and moderate climbs but no more than 6000ft of vertical. That way it can be a challenge to ride fast but it won't leave anyone behind. Sunscreen is a nice item to offer at the sags. From the halfway point on of the century have at least one salty food item at the rest stops. It can be something simple like potato chips.