As hard as it will be at first to REALLY get organized the more prepared you are the less stress and the less he will feel anxious. I'm not sure about you but when people around me feel frustrated I pick up on that and it makes me a little anxious especially if I don't know why. Your son is likely feeling this but doesn't know any other way to vent but with aggression, he can't really express himself like an adult can.
A routine, kids need structure. Wake up, breakfast, activity or chores (3 years is not too young to help), lunch, activity etc.
Have your days planned out and tell them what you will be doing and what they need to do to help.
Also, plenty of exercise, a big source of frustration for kids that young is pent up energy. That is physical and mental exercise. He could be playing sports, doing phonics games, my younger brother liked to memorize US map cities and statistics at that age. Get them outside or into an indoor playgroup.