No, it is not part of the rubrics of the Mass for congregants to greet each other before Mass starts. In fact, it is part of traditional Catholic piety to maintain a reverent silence while in the church, both before and after the liturgy, out of respect for the magnitude of what occurs during the liturgy: the sacramental re-presentation of Christ’s sacrifice on Calvary and Christ’s continuing sacramental presence in the tabernacle. Chatter, however well-intentioned, distracts others from their focus on Christ and from their internal preparation for meeting him in the Mass and in the Eucharist.
It is a praiseworthy goal for your parish to seek to help its congregants feel welcome, but disrupting private prayer before Mass is not the way to do it. If your parish has a social hall, it might be better to encourage the formation of a hospitality group to provide coffee and doughnuts after morning Masses, thereby encouraging congregants to mingle after Mass and outside of the church. If necessary, a discreet mention of the availability of coffee, doughnuts, and camaraderie in the social hall can be made during the announcements at Mass. Notice can also be placed in a church bulletin.
