Hold on to your hats for a few surprises in DMC on music:
30. Singing must be given great importance in all celebrations, but it is to be especially encouraged in every way for Masses celebrated with children, in view of their special affinity for music. [See GIRM 19.] The culture of various peoples and the capabilities of the children present should be taken into account.
Eucharistic acclamations, not the presider dialogues, are given high priority here:
If possible, the acclamations should be sung by the children rather than recited, especially the acclamations that form part of the eucharistic prayer.
Adjustments in the text are permitted, if approved by “territorial authority.” And yes, Musicam Sacram permitted this:
31. To facilitate the children’s participation in singing the Gloria, Credo, Sanctus, and Agnus Dei, it is permissible to use with the melodies appropriate vernacular texts, accepted by competent authority, even if these do not correspond exactly to the liturgical texts. [See Musicam Sacram 55.]
A positive note on musical instruments:
32. The use of “musical instruments can add a great deal” in Masses with children, especially if they are played by the children themselves. [Musicam Sacram 62.] The playing of instruments will help sustain the singing or to encourage the reflection of the children; sometimes in their own fashion instruments express festive joy and the praise of God.
And a caution about overpowering or distracting music:
Care should always be taken, however, that the musical accompaniment does not overpower the singing or become a distraction rather than a help to the children. Music should correspond to the purpose intended for the different periods at which it is played during the Mass.
And a curious concession to recorded music:
With these precautions and with due and special discretion, recorded music may also be used in Masses with children, in accord with norms established by the conferences of bishops.