I would definitely call those peak times - all 3. You might do okay with 11:30 most places, 11-11:15 would be better.
6 PM and on becomes prime dining time. And 8 AM is definitely busy at the resort eateries.
We try to eat lunch in that 11:00-11:15 time frame (arriving @ the restaurant), dinner around 5:00-5:30. Breakfast we don't usually do much for - or eat something in the room, or after we are in the parks, or have a late in the morning TS reservation as kind of a brunch.