I've always thought some of NMA's songs sound like they could be pretty well some old traditional folk songs. SUNSET for example. I could easily imagine there 3 acoustic guitars more, violins and feet stomping the floor of old barn house, while everyone are dancing. But of course it depends on a person what imaginations you get. Although there are quite many folky instruments already, it's still a bit more 'rock' type of song and there's the thin line that makes NMA exceptional because they don't have to underline their influences: no need to make cheap tricks and try to give something what would be evident.
Another piece is GHOST TRAIN from Justin's solo career that could easily fit to children's song or lullaby section despite the lyrics.