Along with what the other posters have said, here's the low down on Free Dining (in September anyways):
- Disney Resorts will be more crowded as people have to stay on site for Free Dining. You may notice the levels in the food court, busses, around the pool, etc. We generally spend most of our times out at the parks and get a rental car, so it didn't bother us.
- Restaurants: Generally, they will be busy. As long as you have your ADRs for table service, you will be fine. For counter service, try eating at off peak hours - try to avoid standing in the longest lines right around noon and 5 - 6 p.m.
- Parks: Crowds will be light! Last September, about the same week you are going, we enjoyed walking on some rides, and except for the big headliners, we almost never waited more than 15 minutes for an attraction. And for the big ones, like Soarin, etc - use FASTPASS, and save yourself the wait. Honestly, the whole week we were there, the longest wait we ever had was about 25 minutes one night for Peter Pan.
Enjoy your trip!