Hi Lindy,
I love October as a time of year to visit Walt Disney World. We try to take a trip to Walt Disney World during October or November each year, in large part because the crowds are not too high and the weather is lovely.
There may be a slight increase in attendance compared to other times in October due to Columbus Day; however, crowds won't be nearly as high as they are during times that most children are out of school such as summer or over Spring Break. Not all school districts have the day off for Columbus Day, so if you are able to leverage that to visit, I think it's a great time to go. For specific predictions on predicted crowd levels for specific days, I recommend touringplans.com.
In my opinion, the weather in October is lovely. The highs are in the mid-eighties Fahrenheit and lows at night are in the mid-sixties, on average. It also doesn't tend to be too rainy in October.
There are some wonderful events at Walt Disney World in October. The
Epcot International Food and Wine Festival will be taking place. At this event, you can explore cuisine from around the world at the World Showcase in Epcot. You also might want to get tickets for
Mickey's Not So Scary Halloween Party, a special event which takes place in the Magic Kingdom Park on select nights. You can come in costume and trick or treat around the Magic Kingdom Park.
I hope you have a wonderful trip, Lindy. Please do not hesitate to ask if you have any further questions!