I agree with you on your first point where you say that the best way to get concepts is by breaking things. But two to five minutes for explaining such CS concepts as variables, functions, and even operators may prove to be nothing more than just a fleeting moment, especially if you are dealing with a group.
Do you mean 8-16 as an age range or a number of students in the class?
Also, not all kids get excited at the first sight of scale. It often requires taking time to explain things and give different examples of this phenomenon.