From the Directory for Masses with Children, Chapter 3 “Masses with Children in Which Only a Few Adults Participate”:
“40. … It is sometimes permissible to omit one or other element of the introductory rite or perhaps to expand another element. 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.”
Chapter 2 has the heading “Masses with Adults in Which Children Also Participate”. It includes in the last sentence: “19. … Wherever the bishop permits, in addition to the adaptations already provided in the Order of Mass, one or other of the particular adaptations described later in the Directory may be employed in a Mass celebrated with adults in which children also participate.”
The General Instruction of the Roman Missal includes:
“46. … In certain celebrations that are combined with Mass according to the norms of liturgical books, the Introductory Rites are omitted or take place in a particular way.”
“51. … From time to time on Sundays, especially in Easter Time, instead of the customary Penitential Act, the blessing and sprinkling of water may take place as a reminder of Baptism.”