Hello, Kimberley,
During the month of October, the average temperature is 75 degrees with an average high of 84 degrees. So for my family, that would be warm enough to visit the water parks. Prior to your visit, I'd encourage you to follow the weather forecast on a website such as www.weather.com to see how the temperatures are looking for you.
As for some attractions being closed, there is always that possibility whenever visiting WDW since they are always working on making things better and improving attractions for guests. You may also find some hours at the Magic Kingdom shorter when the park closes early for Mickey's Not so Scary Halloween Party. If you visit the
Park Hours, you can explore the different park hours in October of this year to see how the hours compare as well as the refurbishments.
We have visited WDW several times in October, and I have always enjoyed that time. It isn't as hot, but still comfortable and the crowds are a bit lighter. With the
Mickey's Not so Scary Halloween Party and
Epcot International Food and Wine Festival, it makes the trip that much more special.
If you have more questions when planning your first WDW trip, please let us know. We are happy to help!