Hi Quinn,
You've chosen a great time to visit Disney World. Weather at the end of September is generally in the 80's, with an occasional afternoon shower. Crowds are usually moderate because many schools are back in session.
Be sure to book some Advanced Dining Reservations ahead of time to significantly reduce your wait at dinner time. Your little girl would love character meals. I recommend Cinderella's Royal Table, it's perfect for little princesses. In addition, Chef Mickey's, Crystal Palace and Donald's Safari Breakfast are all wonderful as well.
If you'd like to surprise your husband and little girl with something special waiting in the room, see
HERE. There are romantic gifts, as well as special treats for your daughter.
Hope this helps and have a wonderful vacation,
Kaylene