I am a newbie too! You must be getting excited for your trip! I am going 4 days after you leave so we are kinda in the same boat. I hope some of the more experienced DIS-ers chime in, but tis is what I am expecting.
I am expecting busier and more crowds than was typical for Septembers in the past. I do not think it is going to be a "ghost town" as one site had as a predication, but it is not going to be as busy as summer by any means!
So....I am preparing for "mid/moderate" crowd levels. I expect to use the FP system. I do have a plan on how we will to our first day at CA. I also expect that CA will balance out the crowds that are there so DL is not going to feel like a nut house by any means. Really I am only expecting to feel my blood pressure rising is in Cars Land. It is going to feel busy in there no mater what. But it will be fun!!!!!
If it is less busy than I am prepared for it will be a bonus!