Chapter III, Part 8. Parts of the Mass
38. The general structure of the Mass, which "is made up as it were of the liturgy of the word and the liturgy of the eucharist," should always be maintained, as should certain rites to open and conclude the celebration.  Within individual parts of the celebration, the adaptations that follow seem necessary if children are truly to experience, in their own way and according to the psychological patterns of childhood, "the mystery of faith . . . by means of rites and prayers." 
39. Some rites and texts should never be adapted for children lest the difference between Masses with children and the Masses with adults becomes too pronounced.  these are "the acclamations and the responses to the priest's greeting,"  the Lord's Prayer, and the Trinitarian formulary at the end of the blessing with which the priest concludes the Mass. It is urged, moreover, that children should become accustomed to the Nicene Creed little by little, the right to use the Apostles' Creed indicated in no. 49 remaining intact.
A. Introductory Rites
40. The introductory rite of Mass has as its purpose "that the faithful coming together take on the form of a community and prepare themselves to listen to God's word and celebrate the eucharist properly."  Therefore every effort should be made to create this disposition in the children and not to jeopardize it by any excess of rites in this part of Mass.
It is sometimes proper to omit one or other element of the introductory rite or perhaps to expand one of the elements. There should always be at least some introductory element, which is completed by the opening prayer. In choosing individual elements, care should be taken that each one be used from time to time and that none be entirely neglected.
B. Reading and Explanation of the Word of God
41. Since readings taken from holy Scripture "form the main part of the liturgy of the word,"  even in Masses celebrated with children biblical reading should never be omitted.
42. With regard to the number of readings on Sundays and holy days, the decrees of the conferences of bishops are to be observed. If three or even two readings appointed on Sundays or weekdays can be understood by children only with difficulty, it is permissible to read two or only one of them, but the reading of the gospel should never be omitted.
43. If all the readings assigned to the day seem to be unsuited to the capacity of the children, it is permissible to choose readings or a reading either from the Lectionary of the Roman Missal or directly from the Bible, but taking into account the liturgical seasons. It is recommended, moreover, that the individual conferences of bishops see to the composition of lectionaries for Masses with children.
If, because of the limited capabilities of the children, it seems necessary to omit one or other verse of biblical reading, this should be done cautiously and in such a way "that the meaning of the text or the intent and, as it were, style of the Scriptures are not distorted." 
44. In the choice of readings the criterion to be followed is the quality rather than the quantity of the texts from the Scriptures. A shorter reading is not as such always more suited to children than a lengthy reading. Everything depends on the spiritual advantage that the reading can bring to the children.
45. In the biblical texts "God is speaking to his people . . . and Christ is present to the faithful through his own word."  Paraphrases of Scripture should therefore be avoided. On the other hand, the use of translations that may already exist for the catechesis of children and that are accepted by the competent authority is recommended.
46. Verses of psalms, carefully selected in accord with the understanding of children, or singing in the form of psalmody or the Alleluia with a simple verse should be sung between the readings. The children should always have a part in this singing, but sometimes a reflective silence may be substituted for the singing.
If only a single reading is chosen, the singing may follow the homily.
47. All the elements that will help to explain the readings should be given great consideration so that the children may make the biblical readings their own and may come more and more to appreciate the value of God's word.
Among such elements are the introductory comments that may precede the readings  and that by explaining the context or by introducing the text itself help the children to listen better and more fruitfully. The interpretation and explanation of the readings from the Scriptures in the Mass on a saint's day may include an account of the saint's life, not only in the homily but even before the readings in the form of an introduction.
When the text of the readings lends itself to this, it may be helpful to have the children read it with parts distributed among them, as is provided for the reading of the Lord's passion during Holy Week.
48. The homily explaining the word of God should be given great prominence in all Masses with children. Sometimes the homily intended for children should become a dialogue with them, unless it si preferred that they should listen in silence.
49. If the profession of faith occurs at the end of the liturgy of the word, the Apostles' Creed may be used with children, especially because it is part of their catechetical formation.
C. Presidential Prayers
50. The priest is permitted to choose from the Roman Missal texts of presidential prayers more suited to children, so that he may truly associate the children with himself. But he is to take into account the liturgical season.
51. Since these prayers were composed for adult Christians, however, the principle simply of choosing from among them does not serve the purpose of having the children regard the prayers as an expression of their own life and religious experience.  If this is the case, the text of prayers of the Roman Missal may be adapted to the needs of children, but this should be done in such a way that, preserving the purpose of the prayer and to some extent its substance as well, the priest avoids anything that is foreign to the literary genre of a presidential prayer, such as moral exhortations or a childish manner of speech.
52. The eucharistic prayer is of the greatest importance in the eucharist celebrated with children because it is the high point of the entire celebration.  Much depends on the manner in which the priest proclaims this prayer  and on the way the children take part by listening and making their acclamations.
The disposition of mind required for this central part of the celebration and the calm and reverence with which everything is done must make the children as attentive as possible. Their attention should be on the real presence of Christ on the altar under the elements of bread and wine, on his offering, on the thanksgiving through Him and with Him and in Him, and on the Church's offering, which is made during the prayer and by which the faithful offer themselves and their lives with Christ to the eternal Father in the Holy Spirit.
For the present, the four eucharistic prayers approved by the supreme authority for Masses with adults and introduced into liturgical use are to be employed until the Apostolic See makes other provision for Masses with children.
D. Rites Before Communion
53. When the eucharistic prayer has ended, the Lord's Prayer, the breaking of bread, and the invitation to communion should always follow,  that is, the elements that have the principal significance in the structure of this part of the Mass.
E. Communion and the Following Rites
54. Everything should be done so that the children who are properly disposed and who have already been admitted to the eucharist may go to the holy table calmly and with recollection and thus take part fully in the eucharistic mystery. If possible, there should be singing, suited to the children, during the communion procession. 
The comments that precede the final blessing  are important in Masses with children. Before they are dismissed they need some repetition and application of what they have heard, but this should be done in a very few words. In particular, this is the appropriate time to express the connection between the liturgy and life.