I hope you have all your restaurant reservations made already...the popular places like Chef Mickey's book up 6 months in advance. September is slow for crowd size in parks, but BUSY in the popular restaurants due to Free Dining bookings. There's no showing up and putting your name in at the popular park & resort restaurants. IF they're taking names, you could be waiting as long as 90-120 minutes for a table. Not fun with little ones. If you do not have restaurant reservations yet, get on-line and book immediately (or call Disney) Remember when you're booking to include both kids on the reservation (even though you don't have to pay for the toddler's meals...they will book you at a table for 4 to allow room for high chairs, infant seat, etc.)
Now if you have a car and can go to the out-lying not-super-popular resort restaurants then you can wing it, even during Free Dining.