How would you explain Bernoulli to a nine year old?
Bernoulli's principle is probably not the best starting point to explain lift generation, especially if you do not first explain the origin of the Bernoulli effect! Naïve invocations of Bernoulli have led to a number of incorrect 'explanations' that are quite widely circulated, such as the idea that air flows faster over the upper surface of a wing because it is more curved that the lower, and thus creates a longer path. If this explanation were correct, paper airplanes and inverted flight would be impossible.

Bernoulli's principle is a consequence of Newton's laws of motion applied to incompressible fluid flow. To explain lift, you can start by invoking Newton directly, by observing that lift is the reaction to the wing's downwards acceleration of the airflow around it. Bernoulli enters the picture when you get to calculating the changes in pressure and velocity within that airflow.

From this perspective, we can see that while blowing air over a wing would create some lift, as the wing will deflect at least some of that airflow downwards, you would get more lift by pointing the fan directly downwards. This is, of course, what a helicopter does, and it takes a lot of power, so wing-blowing, being a less-effective way of generating lift, would require even more. If, instead, you use the fan as a propeller, you only have to produce enough thrust to counter the drag, which may be as little as 1/50 of the lift.