A lecture in the making. Two friends discuss how to
explain radio to their children. post 
on demos ...
It has been my experience that ham radio demonstrations are a crushing bore for kids. The legal restrictions and accepted operating practice conspire to make it so. Not to mention that the only other hams on in the daytime are retired.
on waves ...
A key to understanding propagation is to realize that energy is transferred both forward and backwards, say from a collapsing electrical field to growing magnetic fields both ahead and behind the wave front. However, the backward energy transfer is just enough to cancel out residual fields so that the net is a forward motion. Like the springy loops twisting at each other as we wave a slinky.
on detectors ...
My radio has two advantages over the light bulb. First the ion cloud is a better reflector than the average cumulous, and second, my radio concentrates all of the energy into an extremely narrow portion of the spectrum overpowering what little noise falls in there. The receiver "knows" something about my signal that helps it distinguish it from noise.
Likewise, the receiver of a spread spectrum signal "knows" something else (the pseudo-random code) that lets it separate the desired signal from uncorrelated noise. The trouble with a light bulb is that it both broadband and incoherent. There is nothing to know that would tell it from any other light in the sky.
See Weak Signal