What is the ruling on clapping at young children's performances (ages 5-12)?

So there's no issue with clapping nowadays. There is a verse in the Quran where Allah talks about how those who are non-Muslim at the time used to worship by clapping and whistling. However, nowadays the context is different. Nobody claps as a form of trying to worship somebody. Your clapping often is encouragement or as a form of warning and so therefore, there's no issue, inshallah, with clapping nowadays.