Some people do like to rely on predictability and comfort when they come to church.
On the other hand, if your members have strong preference for a particular Mass, that should be taken into account. Occasionally, if not more often, it might be good to have the experience of a different Mass, a holy day perhaps. Your desire for a schedule is quite valid, and not at all selfish. Maybe a meeting of all group leaders so the pastor and music director can explain their concerns and listen to yours. Some people do like to rely on predictability and comfort when they come to church.