Al Salamu 'Alaykum.
We used to make toys out of dyed wool for the children and keep them with us so if the children asked us for food we would give them the toys to distract them until they completed their fast.
Sahîh Muslim. A similar narration is also in Sahîh Al-Bukhârî.
Al-Nawawî states in his commentary on Sahîh Muslim:
In this narration we are shown that children should be trained to do acts of obedience and made used to doing worship; although they are not legally bound.
Taken from Sayings of the Salaf.