We are going in September and I am still changing some of mine, so there are times available. I have been surprised at some of the good spots/times I have gotten. I have also dropped some very good picks like Le Cellier. I think you will have great difficulty walking up and getting in at many places, especially in the parks, so it would be best to try and book them all now. This is my fifth trip during FD and I would never show up without ADRs.
If you are only trying dinner times, maybe look at lunch times, many places offer the same menu. Another thought is a great breakfast buffet or all you can eat, where you will get alot of food with a variety of items to get through to an early CS dinner, snacking in between. Boma breakfast or All you can eat skillet at WCC for breakfast or lunch at Biergarten are a few. The Biergarten never appealed to me, but I just ate there in May and it was wonderful. I would much rather eat well early in day than have a heavy dinner at night. I am often playing on computer after midnight and that is when I have picked up some nice times, so try in off hours. And don't hesitate to keep trying after arrival. I once dropped CRT just two days ahead while we were there along with a couple others.
I just try to be flexible and open to trying new things, often I have been pleasantly surprised.