Careful - this explanation isn't just a simplification - it's outright wrong. Applying differential power to the front and rear rotors is how you initiate a pitch moment. You must reverse the pitch moment when the drone is at the desired attitude. This attitude may cause the drone to accelerate in a given direction. When the drone has reached the desired speed the attitude change must also be undone (but not completely, due to drag) to kill the acceleration. So to bring a drone from a hover to a steady forward velocity requires four applications of differential power - two one way, and two the other way. It's not even true that the rear ones expend more total power over the course of the maneuver - it's symmetrical.
It's a neat example of Newton's First law, and also a good opportunity to explore a little about 0-order, 1-order, 2-order motion (you might explore what kicking your foot does when 1) walking 2) riding a skateboard, 3) driving a car). But if you think it's too complicated, better to avoid it entirely than give the wrong idea.
(A related question you can ask - when an airplane is in a steady climb, which is greater - the lift on the wings, or the weight of the plane? Answer: they are the same! Otherwise the aircraft would be accelerating up or down.)
So I usually start with "what if the back rotors go a little faster?": it tips it forward, beginning a series of operations leading forward motion (like turning the wheel of a car away from center -- what happens if you keep it turned?)
I've also found that words matter: "attitude", "differential", "pitch", "velocity", "acceleration", etc. -- may be hard to access, and simpler terms like "faster", "slower", "speed", "tipped" are usually more broadly understood.
A recent such explanation episode got me thinking more about this - I'd recently got a pair of noise cancelling headphones and wanted to demo it to my kids. In an inspired (or dumb) moment, I introduced it to them like this - "you know headphones play music right, this one plays silence." I'd like to think I caught a whif of both understanding and "what the .." in their expressions :D