Du'a for children's faith and guidance

اللَّهُمَّ حَبِّبْ إِلَيْهِمُ الْإِيمَانَ وَزَيِّنْهُ فِي قُلُوبِهِمْ، وَكَرِّهْ إِلَيْهِمُ الْكُفْرَ وَالْفُسُوقَ وَالْعِصْيَانَ، وَاجْعَلْهُمْ مِنَ الرَّاشِدِينَ

Allahumma habbib ilayhimul-iman, wa zayyinhu fi qulubihim, wa karrih ilayhimul-kufra wal-fusuqa wal-'isyan, waj'alhum minar-rashidin

O Allah, endear faith to them and beautify it in their hearts, and make disbelief, defiance, and disobedience hateful to them, and make them among the rightly guided.

A general supplication adapting phrasing from the Qur'an (49:7).