Lay people who serve at Mass are only supposed to do one role (EMHC, reader, altar server). I think there can be exceptions, for example when a seminarian is assigned to a parish, but that’s the general rule.
Is there are official preference here?
The Ceremonial of Bishops(Liturgical Press, 1989, ISBN 0-8146-1818-9) has for the Stational Mass of the Diocesan Bishop, in the entrance procession:
"128. … censerbearer carrying a censer with burning incense;
- an acolyte carrying the cross, with the image to the front, walks between seven other acolytes, or at least two, carrying candlesticks with lighted candles;"
So for this Mass there is encouragement for lots of lay ministers. The point is also made in this book:
"19. In every liturgical assembly, and especially one at which the bishop presides, all those present have the right and duty to carry out their parts in the different ways corresponding to their differences in order and office. Each one, therefore, minister or layperson, should do all of, but only, those parts which pertain to that office by the nature of the rite and the principles of liturgy. [footnote 25: See Sacrosanctum Concilium, art. 28 …] This way of celebration manifests the Church in its variety of orders and ministries as a body whose individual members form a unity. [footnote 26: See Sacrosanctum Concilium, art. 26].
Another official document encouraging lots of people doing lots of ministries in the Mass is the 1973 Directory for Masses with Children, in Chapter 3 “Masses with Children in Which Only a Few Adults Participate”:
“
Offices and Ministries in the Celebration
22. The principle of active and conscious participation are in a sense even more significant for Masses celebrated with children. Every effort should therefore be made to increase this participation and to make it more intense. For this reason as many children as possible should have special parts in the celebration: for example, preparing the place and the altar (see no. 29), acting as cantor (see no. 24), singing in a choir, playing musical instruments (see no. 32), proclaiming the readings (see nos. 24 and 47), responding during the homily (see no. 48), reciting the intentions of the general intercessions, bringing the gifts to the altar, and performing similar activities in accord with the usage of various peoples (see no. 34).”
So, at least for some Masses, there is an ideal of lots of lay ministers doing lots of things. On the other hand, there are specialists, the instituted ministers whose ministry is to be respected. As expressed in the General Introduction to the Lectionary, n. 51:
“The ministry of reader, conferred through a liturgical rite, must be held in respect. When there are instituted readers available, they are to carry out their office at least on Sundays and festive days, especially at the principal Mass of the day.”
Another aspect is the practicalities. Lots of people doing lots of ministries requires a lot of training, assessment of skills, assessment of the suitability of individuals, and coordination. Decisions about whether this is worthwhile are up to the parish priest.
From the 2002 General Instruction of the Roman Missal (GIRM) approved for the USA, which can be accessed from
romanrite.com/girm.html :
"107. The liturgical duties that are not proper to the priest or the deacon and are listed above (cf. nos. 100-106) may also be entrusted by a liturgical blessing or a temporary deputation to suitable lay persons chosen by the pastor or rector of the church.89 All should observe the norms established by the Bishop for his diocese regarding the office of those who serve the priest at the altar. …
- If there are several persons present who are able to exercise the same ministry, nothing forbids their distributing among themselves and performing different parts of the same ministry or duty. For example, one deacon may be assigned to take the sung parts, another to serve at the altar; if there are several readings, it is well to distribute them among a number of lectors. The same applies for the other ministries. But it is not at all appropriate that several persons divide a single element of the celebration among themselves, e.g., that the same reading be proclaimed by two lectors, one after the other, except as far as the Passion of the Lord is concerned.
- If only one minister is present at a Mass with a congregation, that minister may exercise several different duties."