I think you are wonderful to be making this for her.
FWIW, I like the idea of doing a lot of free motion circles very tightly together in the corner leaving the center completely stitch free and punching a proper hole through it where you finger fits. That is what her son did and what she wants to replicate I think. I think she wants the fraying so I don’t think a button hole will work.....although I really prefer the buttonhole.