I also noticed they updated or changed the "Lord Grant us Priests" prayer. They added a new line at the end, "O Lord, grant us many holy Catholic families".
It's good for everyone to pray for priests and vocations -- that is supernatural. It is above and a bit against nature. But marrying is the way of all flesh; the way of nature. We don't need to pray for couples to pair off into marriages. At least not on the same level with praying for priests.
Let's put it this way: if we don't encourage vocations, or pray for more priests, all the couples in your parish WILL get married. Like I said, it's the way of all flesh. The default path for human beings. Everyone who finds a suitable spouse naturally gets married.
Praying for vocations on a weekly (or daily) basis is one way to instill in our children that we would love to have our prayers answered by having a vocation from among our own children. Besides beseeching God for the blessing of more vocations, it also teaches our children the implicit truth that vocations are a blessing from God. That's why I like this prayer, and that's why the prayer exists.
Placing marriage on par with priesthood/religious vocations is just WRONG. St. Paul clearly said that the religious life (which includes the Priesthood) is superior to the married life. There is an objective superiority of virginity over marriage. So it seems like we have here a subtle Novus Ordo error creeping in to the SSPX.
The key to this issue is that STRICTLY SPEAKING marriage is not a vocation. It's the absence of a vocation. Again, it's going the human route, the way of all flesh. It's noble when elevated to a sacrament, but it's not a vocation strictly speaking.
It's only a vocation in the broad sense, as in "one's calling". Some are called to be single, some married, and some to the religious life or priesthood. My "vocation" or "calling" in this sense is to the field of computer programming. But I wouldn't place my "vocation" of computer programmer next to Fr. Zendejas' vocation to be a priest. The two words "vocation" are the same, and have the same letters and pronunciation, but they have a different meaning. One is being used in the strict sense, and the other in only a broad sense.
I don't like to disagree with anything you say but in this particular instance, I have to slightly disagree. Here are my thoughts:
Firstly, marriage is under attack. Whether it is civilly, through the government mandates, or by Rome, through the relaxation of annulment regulations. The family is, la petite église, the small church. Imagine what the world would look like if every Catholic family had at its model the Martin family, parents of Saint Thérèse de Lisieux. Sister Lucia of Fatima is quoted as saying that, "The final confrontation between the Lord and satan will be over marriage and the family." We must constantly pray for families, both formally/publically as a church and privately, in our own devotions. I believe the addition of the extra line behind the other petitions is a formal way for us, as a Church, to constantly pray for this fundamentally important cause. It takes away nothing from the other petitions.
Secondly, I disagree with the notion that the extra petition discourages our children to discern the religious life. Just as you said, the petition will teach our children that holy families are a gift and blessing from God. Note that the petition uses the adjectives "many," "holy," and "Catholic." We ask Our Blessed Lord for not just "families" or "children" or "households," we ask for "CATHOLIC," "HOLY" families, families that will produce vocations precisely because they will the small church that will foster the vocations. I dare to say that without "Holy" and "Catholic" families, we will not have any vocations.
Thirdly, and this point is up for discussion, I disagree with the notion that marriage is not a vocation. Yes, the apostle Paul as well many Popes, from Pius XII to John Paul II, have always taught the superiority of religious life. John Paul II stated, "The profession of virginity or celibacy enables consecrated persons to share more directly in the mystery of this marriage, the nuptual union of Christ and His Church." In a similar way, a vocation to marriage is a call to holiness, a rejection of the culture of death and the present forces that wish to destroy the Holy Bond. Marriage is not the absence of a vocation, it IS a vocation in itself. A remark that marriage is "dirty" or should be avoided is what the gnostics believed. Our work is also a vocation for God created us ut operaretur et custodiret illum, to work, "as man is born to labour and the bird to fly"[Job5:7]. Our work is also a calling of God, another method of sanctification for it is in our work, your work as a computer programmer or my work as a student, with the right intentions, becomes where we practice our faith, our sacrifice.
I don't think adding "Lord, grant us many holy Catholic families" is an error or will somehow lead our children to all become married. If they are called to the religious life, God will give them the graces needed to make it happen if it is His Will. We must constantly pray for more Catholic Holy families everywhere.