Listen and try first
Let the child hear the low and high E strings. Count four steady beats and pluck one string on each beat. Then find open E and a note at fret 3 on the interactive fretboard. An abstract note becomes a sound.
From note to song
Choose a simple public-domain tune and learn one short phrase at a time. Sing along and repeat only the difficult notes. Finish with something that already works, without rushing the tempo.
Must my child learn chords immediately?
No. A single-note melody is real guitar playing too; chords can come later.