If the last couple of years are anything to go by, the weekend October crowds are VERY manageable, and if the weather is cooler, a LARGE percentage of rides are walk on. This has been my experience the last two years (especially in the mornings), so Fast pass could be a decision on the day option..shouldn't really need to book it beforehand. It gets VERY busy in the afternoon/evenings in the run up to Halloween but not so much early in the month. If you arrive first thing for park opening you will definitely have a good couple of hours before it gets even remotely busy. In a way you should HOPE for cold weather as that seems to keep a lot of the GP away!
As for itinerary...everyone has their own opinion.....personally my only guide is to do the Guardian first, as it does not have fastpass options, can be temperamental and has an awkward queue if it gets too long (outside the mountain!). Apart from that...if the park is quiet, you can get everthing done pretty easily. Leviathan is a good start point (outwith Guardian) as it puts you in a good area geographically to work around the park in either direction. If you start at the other side (Flight Deck and Time Warp)...you are starting with two of the...shall we say not so popular..rides in the park and it can be pretty off putting getting slammed around on Flight deck first up!!
Don't forget to try the flat rides as CW has a pretty good selection of those. If Sledge hammer is working...I would thoroughly recommend it.
Hope you enjoy your trip.
Thank you so much for your help!!! Hoping it's somewhat cold when we go!!