Be prepared for heat. Much of the country is cooling down by October 1st, not central Florida though. We hit record highs over Columbus Day weekend when we were there last year. The heat index was over 100. What's funny about that is that mid-September of last year, if you go back and read the threads from last year, was very cool and rainy. The heat came back with a vengeance.
Keep in mind that early October is still active hurricane season, and it's possible, (although not likely), that a tropical storm system may soak your entire vacation.
The crowds should be quite manageable until the three days before you leave. The masses will descend on WDW the 9th, 10th and 11th. Personally, I found fall break, (that weekend), to be even more crowded than spring break. Not Christmas crowded, but you will definitely notice the difference.