Maybe this will help him learn how to hold the guitar correctly.
So, I started out trying to put a shoelace through the little holes but it wouldn't fit. So, I found some ribbon and made a couple loops.
I just hand sewed them on and turned so the sewn part is inside the hole.
Tada! A guitar strap! Just tie the shoelace to the loops of ribbon- very adjustable! As with everything that goes around the neck, make sure to always watch your baby so they don't strangle themselves.