What we do here with our 3yr old twins and 6yr old. We fill sippy cups the night before with milk, and everyone has a Nutrigrain Bar before getting dressed or after depending on how fast or slow we are moving. The other breakfast bars we love is Quaker Oat Breakfast Bars, it claims its the equivalent of a bowl of oatmeal. It has 220 calories that and a milk is a good way to start the morning. They can eat while you are exercising. After you exercise start getting them ready and they can finish eating after they are dressed if they aren't finished already. Mine eat in their rooms. I bring the breakfast bars upstairs, and they drink their milk either in the car on the way, or after they get dressed. Its so doable. So lay the breakfast bars out with their clothes. I even untie shoe laces at night to shave a few seconds off our morning. Granola bars don't have enough calories most have about 100 calories or less.
The first week is tough, you will get your routine together I am sure in another week or so.