Casting for Nativity Plays

I'm thanking the heavens as I type that I've never had to cast one of these legendary affairs, but the article is just too funny:

Come Christmas, there are always those cynics who dismiss infant nativity plays as pointless charades. What lessons, they ask, are to be learnt in the modern age from watching kids trying to work out what a "virgin's womb" is and how not to "abhor" it? The answer is many, for all concerned – not in the tale itself, but in the telling.

"Anyone can be a Shepherd, but there's only One Mary"