Du'a for children's devotion

اللَّهُمَّ اشْغَلْ قَلْبَهُمْ بِحُبِّكَ، وَلِسَانَهُمْ بِذِكْرِكَ، وَبَدَنَهُمْ بِطَاعَتِكَ

Allahummash-ghal qalbahum bihubbik, wa lisanahum bidhikrik, wa badanahum bita'atik

O Allah, occupy their hearts with Your love, their tongues with Your remembrance, and their bodies with Your obedience.

A general supplication, not a narration from the Prophet (peace be upon him).