Knott's Scary Farm was my favorite October event growing up.
Knott's is a wonderful park. Very relaxing and we have never really run into bad crowds. Don't miss the log ride, it is great! The train ride is very exciting too. If you have little ones Camp Snoopy is wonderful.
Try the Knott's Berry Punch or Boysenberry Punch- this is so yummy and Knott's is known for it. Is the all you can eat bbq going on? that sounded like a good deal! Save some time to poke around Ghost town, and talk to the jailer and then go around to see the prisoner. Also check to see if they are doing tricks in the magic shop.
My kids love to pan for gold and to watch the Geodes being opened at the geode shop (those round rocks that are so pretty inside).
If you are not having bbq try the fried chicken. Don't try the Mexican food, I can not see how they can be in So Cal and have such bad Mexican food...