we have been that week in Oct a few times and that week in Nov last month as it was our DD2's first trip. I was debating the same time frames but went with Nov so she could see the icicle lights on the castle.. gorgeous!, the christmas decorations, festival of dancing lights, and the whole atmosphere of Christmas time at Disney. It was perfect and DD was so cute wearing her Christmas dresses. The weather was mild and mid week was even chilly. At 2, Christmas decor was way more exciting than Halloween (which was my favorite time to go, b/c of my bday and going to the halloween party), but for you pick what your DD is more into.. halloween or Christmas. The crowds were heavy at the start of our week and then light at the end. We had FP+ and regular FP's and did stand by with no waits for the large seating shows. We never waited more than 10 minutes for anything and did it all. EMH was amazing at MK we walked on so many rides we were done by 10am and went to our 11 am Grand FLoridian breakfast.
If waterparks are important, better chance for warmer weather in Oct but Typhoon will be under refurb as always.