It is kind of nice to celebrate your first communion with a group of people who have taken the same initiation courses.
There is no religious requirement to do so, nevertheless. Certainly, if the boy band is really important to these three girls( I am assuming that they are girls), there is nothing stopping them from going to their first communion on the Saturday evening Mass, or even the next week.
It is hard for a group to accommodate the personal schedule of everyone. One would hope that the group will do what they can, but in the end people have to make the choice on their own when it comes to scheduling.
These things happen all the time for a whole variety of reasons, some more mundane that this, some absolutely crucial.