Just back from a trip October 8-20. What a temperature swing! Went from record-breaking heat (90+ every day the first week), to record-breaking cold temperatures (dropped more than 30 degrees in a couple of days)! I hadn't prepared for the cool, windy weather, and just about froze. And this was mid-October!!
Sooooo, my advice is to bring a little bit of everything. Definitely bring a hat, gloves and scarf for everyone - they don't take up much room in luggage, and you'll be so glad to have them if the weather's cold. Be sure to bring long socks -- that was my problem on Sunday. It didn't even reach 60 degrees, and was very windy -- even wearing long sweatpants, my legs froze because all I had brought were short "sneaker" socks. I hunted and hunted and finally found some socks in the Japan pavilion at Epcot. Wish I'd had a hat and gloves, too!
Also, be sure to have a warm jacket (with a wind-breaking feature, not just polarfleece). If it's windy, like at Epcot, that wind can cut right through even fairly warm clothes.
Have fun!