There were no breakfasts in the park going on this past week, the CM at the Santa Fe told me that they were not doing them, even at the weekend, right now. I don't know why - still worth asking though, when you arrive. You never know .
It all depends on hotel capacities, and weather conditions. If the Santa Fe, Cheyenne and the Sequoia Lodge have a very high occupancy level they organise Park Breakfasts to help alleviate the crowds at the hotels during the breakfast rush.
We always try to have breakfast at 7am when it is quieter so we can be in the parks for EMH.