I enjoy Quentin and Quintin. Quincey is too close to a sore throat. Quinn - yeah, a suitable nn, but what about the Mighty Eskimo? Surely the ultimate role model?Benvolio? Not the best way of achieving a son known as Ben, but worse things happen daily.
I had to google this, strange I've never heard of it before! The trouble with Benvolio, for me, is that I don't much like Ben. I'd have to go with Benvolio "Leo", if anything.
I'm so glad I could expand your musical horizons! Nothing like sharing one's favourite earworms ...I rather think that the gravitational force of the first syllable will make Ben the default nn for Benvolio. Pity - Leo is a good choice.