As an opera fan, I would strongly advise against taking your 15 year old daughters to Les Troyens (Berlioz). Apart from massive orchestral forces (typical Berlioz!) there really aren't any 'hummable' arias or choruses, and unless your daughters are into Ancient Greek History, transformed into Romantic opera, I'd think they'd (and possibly you'd) be bored stiff! Just my HO though.