To the best of my knowledge, this is not something the Church has legislated on, so we have to use prudential judgment.
In many Western societies, applause indicates the audience’s approval for a performance. That is why, in traditional Western protocol, applause during church services is generally frowned upon. Music or homilies in church are offered up to God as worship, not to the congregation for its approval. The only exception of which I am aware is during the ordination ceremony for priests. The bishop will usually call for clapping from the congregation as a sign of its support for the newly-ordained priests.
As previously mentioned, this falls in the realm of prudential judgment. While we might wish that the priestly celebrant would prepare children to understand why they won’t be applauded and find other ways to express the parish’s appreciation to liturgical ministers and parish employees (e.g., the bulletin), strictly speaking, the Church does not forbid a priest from encouraging the congregation to applaud. However, you may, if you wish, decline to take part in the applause.
