I don't know about stuf to use,but I want to suggest that his guitar have nylon strings.Kids don't like things that hurt.They don't know anything about getting goog stuff frfom suffering.and stell strings hurt a lot when you're starting.
And what's too bad about chords?I mean,twinkle twinkle can be played with chords.it would probably help him(eventually) ubdeerstand the relationship between chords and scales blah blah blah.
Dunno.