This is how i start the concept with the little ones. It's a musical thought or sentence. You can hsve subphrases. Like with your stories, we can hook the sentences together for longer stories, as short as a picture book, or a long chapter book.
It follows our linguistic idiom. This is why even the instrumental music of different nationalities and eras within sound the way they do.
Your harmonic progression and cadence points snd types will help shape the phrase and inflection via dynamics, vibrato, articulation, etc.