She does it only for the gratification she gets from making the children happier.
Advanced English Dictionary
+noun [U, C] (formal) the state of feeling pleasure when sth goes well for you or when your desires are satisfied; sth that gives you pleasure: sexual gratification + A feed will usually provide instant gratification to a crying baby. + Much to my gratification, my work got a special mention in her speech.
Random quote: Every artist dips his brush in his own soul, and paints his own nature into his pictures.: Henry Ward Beecher