The Amtrak Century on Sept. 9th would be perfect for you, but it's closed to new registrants
AFAIK. I just did the Cool Breeze Century in Ventura, which had a LOT more climbing than the Amtrak will, and it was a lot of fun. Something called the Harvest Ride for Literacy is on Oct. 7, and follows what looks like a similar route to the Cool Breeze:
www.harvestrideforliteracy.org
Good luck,
Bernie