Elastic string will ensure that the bracelet fits, and that it will go on and off easily. As for buttons--it's just as pretty when made with plain ones!
Madeleine first tied a knot, leaving enough length on either side for us to tie the ends together later.
She strung on the first button, through both holes--up through the first, down through the second. She strung on the second button in the same way, so half of it was lying over the first button.
Laced this way, the buttons will overlap, so that the bracelet will be two-sided. Either layer can be the top side; you could do the bottom layer whites, and the top layer blues, and wear it either way.