I don't know that it's the "consensus" here, as I don't ever recall discussing it. But I can say with absolute certainty that I've never been to a Catholic Baptism that didn't take place on a Sunday (and I've literally been to a hundred). To me, it's a joyous, personal holiday, which has always been associated with taking place on a Sunday.
U Talkin' da Me touched on this above, but with respect to the novel some of Puzo's famous sloppy writing is afoot: it talks about Michael being godfather, which would imply Baptism, but they refer to the child being "confirmed", and Confirmation would occur around 7th grade. The child, the elder of Connie and Carlo, might have been of age for his First Communion (age 7 or so).
You'd have godparents for baptism and a "sponsor" for Confirmation. I don't think anyone stands with you at First Communion, as it's usually a large ceremony with all of the kids lined up.
