Sept is value season and Oct is regular season, so there will be a price difference on the resort cost. You should consider checking in by Spet 30 that way your resort cost would be value season each night. And there are alot of discounts out right now for both times..you should read some of Mousesavers to see what discounts might be available to you.
If you want more help give a yell, will need to know more info like ..
how many nights, package or just room only and purchase tickets seperate, how many people and where do you want ot stay.
Rooms are going fast with your timeframe only being about 30 days away.
Lori