Riyad Us-Saliheen (Gardens of the Righteous)

Chapter 136
Greeting the Children

862. Anas (May Allah be pleased with him) reported that he passed by some children and greeted them. Then he said: "Messenger of Allah (PBUH) used to do the same.''
[Al-Bukhari and Muslim].

Commentary: By greeting children, we please their hearts and also vent our modesty. Besides, the importance of  As-Salam is unconsciously felt by them. Above all it is the Sunnah of the Messenger of Allah (PBUH) and so we are supposed to put it into practice.