Marriage vows can be exchanged during a Saturday vigil Mass. In fact, in some places, it is not an uncommon option for couples who are marrying in the Church. My concern in this case is that the couple may not have needed to exchange vows in a Catholic ceremony in the first place; and, if they did need to do so, it should not have occurred at a Mass during which a congregation unfamiliar with the couple and their background could be confused about the Church’s teaching on marriage.
If a couple marries in the Catholic Church and later divorces, that Church marriage is not dissolved by the divorce. All that civil divorce does is to provide for a legal end to common life, for child custody agreements, and for separate households. The couple are still married in the eyes of the Church. If they later reconcile, they do not need to “re-marry” in the Church. All they need to do is to marry civilly so that their marriage will again be recognized by the state. (They don’t even have to do that, but civil remarriage both eliminates a potential source of scandal and can be beneficial for civil legal reasons.) If the couple wants the Church’s blessing upon their reconciliation, they can ask for a nuptial blessing, which can be offered during a Mass if they like.
But if the couple were not married in the Church to begin with, and one or both are Catholics, then they likely are marrying for the first time and this should not have been presented as a remarriage. The fact that this couple has children together does not mean that their first marriage was recognized to be a marriage by the Church. If they were not married before in the Church, divorced, and are now seeking to reconcile, then they are either marrying or convalidating an existing marriage.
Since this situation is so complicated, it seems to me that the priest should have advised this couple to marry or convalidate their marriage in a private ceremony, rather than have allowed them to do so during a Saturday vigil Mass. If the couple was already married in the Church, the nuptial blessing could be done during the Saturday vigil Mass, but there was no need for any “back story” to be given to the congregation as to why the nuptial blessing had been sought.
