Chapter III, Part 5. Gestures
33. In view of the nature of the liturgy as an activity of the entire person and in view of the psychology of children, participation by means of gestures and posture should be strongly encouraged in Masses with children, with due regard for age and local customs. Much depends not only on the actions of the priest,  but also on the manner in which the children conduct themselves as a community.
If, in accord with the norm of the General Instruction of the Roman Missal,  a conference of bishops adapts the congregation's actions at Mass to the mentality of a people, it should take the special condition of children into account or should decide on adaptations that are for children only.
34. Among the actions that are considered under this heading, processions and other activities that involve physical participation deserve special mention.
The children's entering in procession with the priest can serve to help them to experience a sense of the communion that is thus being created.  The participation of at least some children in the procession with the Book of the Gospels makes clear the presence of Christ announcing the word to his people. The procession of children with the chalice and the gifts expresses more clearly the value and meaning of the preparation of the gifts. The communion procession, if properly arranged, helps greatly to develop the children's devotion.