Doubt they'll stay.

By and large, mixed "children's choirs" are a figment of the liberal/feminist imagination. I've never seen a "children's" or "youth" choir with anything like equal numbers of boys and girls. Yes, there are plenty of nominally mixed such choirs out there, but the girls typically outnumber the boys by something like 5 or 6 to one. (I recently re-confirmed this at a concert last weekend in which my city's "Youth Choir" was featured.). Usually, the boys who do sing in the choir are there because their mothers forced them into it or some such. Not only that, these choirs tends to consist mostly of teenage, not younger, girls. Girls' voices don't break; girls just typically sound better as they mature -- more power; more experience. So unless the choir has an arbitrary age cut-off (which it might if it were, say, a grade school choir) the average age will drift upwards over time. So you end up with a choir of middle and high school girls with a tiny smattering of boys. They can sound good (although not as good as well-trained choir of adult women). But they lack that extra sheen of transcendence and purity of the great boy choirs. Prove me wrong! Maybe your parish choir is different. SR