DD was just a couple of months younger than your son on her first trip. We are also in central time. DD is not a morning person by nature. We discovered that with just the one hour time change, pre park opening breakfasts were NOT for us. We tried it once and she just got cranky about getting up early and then was tired and cranky through breakfast and didn't get her energy until we hit the park. We were able to get her there right around rope drop everyday, but what we did was have breakfast in the room as we were getting ready. DH would go get CS and bring it to the room-- she was also picky at that age, so we ordered from garden grocer and had it delivered to the resort so we had things we knew she would eat in the room, so mostly she just ate that for breakfast. I would not waste your morning park hours at breakfast ADRs after opening. The lines are the shortest in the mornings, and with a preschooler it is best to be in the shortest lines possible.
As far as other meals, we typically did a TS lunch around 12:30 (11:30 at home) which was when she typically would want lunch at home. That first trip, I think I booked one for 11:30 and realized that was too early for her internal clock with the time change. We did parks pretty much open to close and discovered that lunch was best. It was a good chance to wind her down from going strong in the morning, and get her to nap in the stroller after lunch. If we did dinner, she usually would be antsy at the table because she was tired- if we kept going in the parks she was fine in the evenings- but it was the sitting down at the dinner table that would do her in.
It is really hard to predict how your child will react at WDW until you have that first trip. We learned to be flexible while we were figuring it out. It is hard now with cancellation penalties-we were lucky enough to be before that. But since you are on a 9 day trip, if you find that something you thought would work definitely will not work, you should have a chance to at least change things around for the later days in your trip. Have a great trip!