We have a two week break - 24 Sept to 9 Oct inclusive. But I don't think the Australian and NZ school holidays will have too much bearing on crowds though I do know quite a few families who are travelling to DW. More Australians and Kiwis go to DL.
Each state or NZ could be +/-1 week on that starting date.
Another group is the year round school systems. Our relatives in KY have year round school and October is a regular break point for them. So its not fall break, but they're out as part of the regular calendar. Its usually mid October.