The end of October is a great time to go. The weather is still warm and the crowds are low. The parks do close early though -- between 6pm and 8pm on weekdays. Are you going to Halloween Horror Nights?
We don't stay onsite, and we usually spend 4-5 days at US/IOA out of a 2 week trip to Orlando. We have been to US/IOA many, many times so we just take things slow, and let our DDs decide the pace of things. The thing we enjoy most about our trips to US/IOA is that we don't have to do the park commando thing. If we sleep in late, we can get to the park at whatever time and still enjoy ourselves. We usually don't enjoy that comfort at WDW which requires much stricter planning.
Have a great trip!!!!