GAW: in the past lots of such kids were institutionalized, likely mistreated, with the financial burden falling on the public. Many of them are not mechuov bechinuch, I would think.
And I’m not intimately familiar with KJ so nothing I say can be used against them, but AFAIK singing cultural songs are allowed as long as it’s not of a religious nature. Think dreidel, dreidel vs. jingle bells.