You never know about October! One year we went and it was about 95 degrees, the next year we went again and it was cool and rained almost everyday! I think you should pack for both scenarios!
We went last year, 9/23 - 9/30, and I was in the same boat, not sure what to pack. So I packed a little of everything! We never wore the pants and jackets, and I wound up having to do laundry halfway through the trip.
I have no idea if last year was typical, or if there even is a typical weather pattern, but to us it felt hot during the day: 80s and 90s, definitely needed t-shirts and shorts. It was cool but pleasant in the evenings: upper 60s/low 70s perhaps, DH and I didn't need jackets, but our boys did.
Our boys even insisted on going swimming in the hotel pool in the evenings (in the dark), but typically only lasted about half an hour because of the chill.
I'll be checking weather.com the week beforehand to make sure there isn't a cold front or rain coming, otherwise I'll plan to pack summer clothes and a jacket/sweatshirt.
you know its true about never knowing what the temp is going to be...but I have a weird feeling that it is still going to be really warm in the day but really cool at night....its now the first part of sept., and its warmer than usual...in the past Ive seen it be mid 80's to high 90's in the day but like I said I think its going to be warmer than usual...
It is so hot here in Vegas I always hope its cool at DL. Keep an eye on the weather channel and the DL website has that days weather on it to help get a closer forcast.