All perfect praise be to Allah, the Lord of the worlds. I testify that there is none worthy of worship except Allah,= and that Muhammad, sallallhu ‘alayhi wa sallam, is His slave and Messenger.
So if the parents left their children with a trustworthy person and they do not fear that anything bad might happen to them, then there is no harm in leaving their children with them, but if going out for da‘wah (proselytization) and leaving their children would cause harm to them, it is impermissible to leave them. ‘Abdullah ibn ‘Amr, may Allah be pleased with them, narrated that the Prophet, sallallahu ‘alayhi wa sallam, said, “It is sufficient sin for a man that he neglects his dependents.” [Abu Dawood]
Allah knows best.