First I’d suggest developing the idea of a wave slowly and carefully, with the building blocks as:
Such an episode moves from a single imitator (mimic, copy-cat) to an array of imitators at different distances. These represent the medium, and arranging them regularly gives a recognisable conventional representation of a wave. The gain is that now children know what the component parts are and how they work together to give this overall pattern.
Then launch into an episode exploring different patterns of motion in the source, still imposing a delay on the imitators depending on their distance from the source. This is the imperative, expressed as a memorable slogan: ”do like me, but later”. The imitators now show a variety of waveforms, and the sequence reinforces the essential component facets of what it is to be a wave.
Not all sources vibrate continuously, so launch into the a third episode moving from a single delayed imitation, to pulses, to wave packets, and back to continuous waves.