I had our ADRs done in spring. A few days ago we added a person to our room, thus needing ADRs for 5 instead of 4. It worked but with alot of shuffling. We are going 8/26-9/2 and almost everything was booked up. We had to get 2 tables for some TSs and switch our planned dinners to breakfasts, breakfasts to lunch, etc. to make it work. It finally did, with a couple of exceptions (Le Cellier, Spoodles) but it took me asking for the alternatives, they definitely weren't offered.
Most TSs didn't have dinners open until after 8:30 p.m. if at all. Hence, we have more breakfasts and lunches now (with our group of 4 we had almost all dinners). All I can say is good luck and keep calling if you don't get what you want now. Also, check out the cancelling ADR thread.