We have gone at this time four times and are going again 10/26 to 11/3.
Pros:
1.It is not miserably hot. In all our times there I can only think of a few days where it was really bad.
2.And, it is not very cold. A few mornings(EE mornings) it is cooler and We wore sweatshirts(with Tshirts underneath) and shorts and were fine. By 10 AM or so the sweatshirts were tied around our waists.
3. Crowds are not as bad as they are in summer. Rarely do we find them unmanageable.
4. Evenings are cool enough for enjoying, but warm enough to swim.
5. Most everything is open..ie not too many rehabs
Cons:
1. Depending on WDW schedule, at some point early November they close one of the water parks. (River Country is usually already closed and we have found that both TL and BB are open while we are there but one closes for the season shortly thereafter.)
2.Crowds are heavier than they used to be in October(but see above..still not bad)
3. MK may close earlier than it would in the summer. Also it closes earlier on the nights when Mickey's Not So Scary Halloween party takes place...we have never found the parks closing so early that it messed up our plans.(and it forces you to get some rest!)
We really like this time of year..I think your family will also.