Another anecdote--brother of my childhood best friend was able to sing the lead in Amahl & the Night Visitors at age 16. He told me years later that being still a boy soprano at that age in small-town America was an unmitigated burden.
Since average age at puberty has been moving steadily earlier anyway I find Nicholas' age quite plausible, tho' convenient from both a Doylist & Watsonian perspective.
thedogsdinner