"KISS" Keep it simple silly. One thing I have learned is to not overload primary students. Unless you are taking the flight controls to talk to them, it usually goes in one ear and out the other. They are so overwhelmed at first, that you need to only say stuff IF IT IS NECESSARY at that moment. Otherwise leave it on the ground and let students make mistakes.
I usually take notes through the flight and do a quick, to the point brief for 5 minutes after the flight. Then what they need to emphasize or practice for next time. It takes a while, but you will see.