In my experience when Masses are celebrated with a children’s choir or a teen band it seems that the focus of the Liturgy shifts from the Sacrifice of the Mass to the children that are singing or the teens that are reading at that Mass.
I know that the children that participate in such events can have a great time doing so, and that they bring great joy to the congregation. Does the joy experienced by the children, and the possible deepening of their faith, make it okay for this to happen, granted that they are within the guidelines of the Church in regards to sacred music?
I note that you say, "within the guidelines of the Church in regards to sacred music".
If that is indeed the case, and the guidelines really are being followed in a deep sense and not merely a shallow, then I trust that the power of the liturgical action, by saying the black and doing the red, will bring about a beneficial effect…. beneficial for religion, that is.
But a lot of rubbish is done in the name of being "within the guidelines". The letter may be followed and the whole core of what the Church is trying to accomplish is violated. Just because the Church provides for flexibility in music styles or provides options and substitutions doesn’t mean that such substitutions are good to be done.
So, I circle back around to the point.
No, it isn’t "okay" simply because they are having a good time or others attain a nice feeling as they watch.
First, Mass isn’t entertainment. The whole point of Holy Mass not to create a human experience, but rather to have an encounter with mystery. Our human experiences at Mass must be conditioned by and predicated on our religious goals.
Music in liturgy has a purpose. Of course it can delight and move and edify. But it must be above all an experience of the sacred, both for the congregation and for those who perform the music. Music is not an add on to the liturgy. It is part of the sacred liturgical action itself. Therefore the texts and music must be conformed to first to the point of Holy Mass. Then other considerations can be considered, such as how the music expresses our cultural, societal, community identity.
The argument might be raised that if children have fun, they will like going to Mass. If they don’t have fun, they won’t go. They will think Mass is boring and religion dreary.
If they think that way, then the problem doesn’t rest in how Mass is being celebrated. It rests in the formation the children received from their parents and their cultural/intellectual formation as well. It might rest in the example, or lack thereof, of parents themselves and how they formed their children, or didn’t form them. Children must be readied and formed over time to be able to accept in a greater and more profound degree what is being offered to them during the sacred action of Holy Mass.
Giving them unworthy, non-liturgical music for the sake of distraction, cuteness, fun, whatever, is another way of lying to them.
A false impression is given of what Mass is and what the virtue of religion is and who they are in the face of fearful mystery.
So.. no. I don’t think it is okay if the motive is simply to "bring joy". Do that in the Church hall afterward.