Meeting before or after Mass can be quite restricted by Mass schedule. We sing at the 10:30, and there is a 9:15, and also a 12:00 noon Mass, so either before of after would not be possible. We also practice one evening a week, and add another for a few weeks before Easter and Cristmas, with summers off.
Maybe you could present the times you are available, and see which is most convenient for the majority of members.
Although this is a misinstry, and not a performance, there does need to be some dedication and practice. Certainly worship is the most important element, but you don’t want the music ministry to sound like a bunch of alley cats. I would also remind members to sing softly if there is a new piece, and they have not attended practice.
Lux