Chapter III, Part 7. Silence
37. Even in Masses with children "silence should be observed at the designated times as part of the celebration"  lest too great a place be given to external action. In their own way children are genuinely capable of reflection. They need some guidance, however, so that they will learn how, in keeping with the different moments of the Mass (for example, after the homily or after communion ), to recollect themselves, meditate briefly, or praise God and pray to Him in their hearts. 
Besides this, with even greater care than in Masses with adults, the liturgical texts should be proclaimed intelligibly and unhurriedly, with the necessary pauses.