… To my knowledge, there does not exist a ritual, for lack of a better word, for sending forth parish missionaries. Thus, any of these “extra-liturgical” activities should be done before the final blessing, but not be imbedded within the context of the Mass and replacing the Creed or any part of the liturgy.
There is a blessing for missionaries in the Book of Blessings (an official liturgical book). I think it is a reasonable interpretation of the ceremony in this book to omit the Creed.
It has in the rubrics: “481 After the homily, all stand. The departing missionaries take places near the celebrant, but in such a way as not to obstruct the people’s view of the rite. With hands outstretched over the missionaries as a group, the celebrant says the prayer of blessing.” (Book of Blessings, Liturgical Press, Minnesota, 1989, ISBN 0-8146-1875-8, page 157).
After the homily is the normal time for all to stand and say the Creed. But it is not mentioned. After the prayer of blessing there is a presentation of crosses to the missionaries with the singing of Psalm 96 or “some other suitable song”. Then: “486 The general intercessions follow, …”.
How is this to be interpreted? Is the omission of the Creed accidental or deliberate? Many other ceremonies mean that the Creed is not said, but state this explicitly. For example if there are the Scrutinies, the liturgical book “Rite of Christian Initiation of Adults” has: “… then, if required, the profession of faith is said. But for pastoral reasons these general intercessions and the profession of faith may be omitted.”
So with the Missionaries’ ceremony I think it is open to interpretation whether it says enough (or omits enough) to overrule the 2002 GIRM: “68. The Creed is to be sung or said by the priest together with the people on Sundays and Solemnities.”
Other ceremonies when the Creed is specifically instructed not to be said:
At the Easter Vigil there is a renewal of baptismal promises, instead of the Creed.
The Creed is not said if there is a baptism in the Mass. (Rite of Baptism for Children, n. 29, The Rites Volume One, Liturgical Press, 1990, ISBN: 0-8146-6015-0, page 374).
And if there is a confirmation at Mass, from the Rite of Confirmation (Rite of Confirmation, n. 31. The Rites Volume One, Liturgical Press, 1990, ISBN: 0-8146-6015-0, page 492).
Nor if there is an ordination of a deacon, priest or bishop in the Mass, from the rite of “Ordination of Deacons, Priests and Bishops” (The Rites Volume Two, Liturgical Press, 1991, ISBN: 0-8146-6037-1, pages 28, 39, 66).
Nor if there is a consecration to a life of virginity in the Mass: (The Rites Volume Two, Liturgical Press, 1991, ISBN: 0-8146-6037-1, page 161, 177).
Nor if there is a rite of religious profession in the Mass,
for a temporary profession by a man: (The Rites Volume Two, Liturgical Press, 1991, ISBN: 0-8146-6037-1, page 213).
the same for a perpetual profession by a man, n. 52(b), page 221.
same if a man renews his vows, n. 83(b), page 233.
same for a women, temporary profession, 25(b), page 252.
same for a women, perpetual profession, 57(b), page 258.
same for a women, renewal of vows, 90(b), page 272.
Nor if there is a blessing of an abbot (The Rites Volume Two, Liturgical Press, 1991, ISBN: 0-8146-6037-1, page 304.
Same for the blessing of an abbess, n. 10, page 314.