I assume you are talking about inquiry as phase in the RCIA process and as questions come up throughout the sessions. Yes you do your best at the time, but a group consensus is not an answer. The best way is to show them how to find answers, and you do this by investigating yourself, as you have done by coming here. Show them for instance how in the gospel Christ initiates the sacraments, the CCC gives the essential teaching, let them know there is canon law whereby the Church interprets and applies those teachings in practical ways and resolves issues.
No we do not discuss individual marriage issues (or other personal areas that may be matter for confession) of the class participants in the class. We can use hypothetical cases for illustration, but we don’t get into specifics of individuals cases.
In this instance, when you go back to the class, refer them back to the initial teaching on the sacraments, specifically the concept of valid matter and form and the ordinary minister of the sacrament. Since the ordinary minister of ordination is the bishop, and the matter and form are his words and actions and use of chrism, with proper intent, those are the basis for judging validity, not the outward actions of the recipient. If the candidate undertook ordination without the proper disposition or intent his actions may be illicit but he is still a priest. The graces of the sacraments may not be available to him if he was in a state of mortal sin at the time, but the objective reality of ordination has taken place. At such time when he returns to a state of grace and assumes the proper disposition, rights and duties of his ordination, he is endowed with the grace to carry them out.
In marriage the matter and form are the vows with proper intention and capacity, and the persons themselves, who must therefore be free to marry, and are themselves the ordinary minister of the sacrament to each other. Therefore not only their own intent and disposition as recipients of a sacrament are essential, but also their intention and proper adherence to the form, words and actions, as the ministers. The matter is the persons themselves who give themselves entirely and freely to each other. In this matrimony differs from the other sacraments where the persons are both ministers and recipients of the sacramental graces and effects.
That is why judging the validity of either sacrament is investigated, explored and judged along different lines.
Should a couple enter into what is outwardly a valid sacramental marriage with faulty intent, or improper disposition, if they later remedy the defect–return to the state of sanctifying grace and will the intended effects and responsibilities of the sacrament–it can become valid at that point. For instance a couple marries in the Church, having been cohabiting for some time, including using ABC, and fully intending to claim the benefits of Christian marriage without accepting all the duties of the state, and even with mental reservations about Church teaching on the sacrament. Later in their life together they come to new appreciation and even without formally renewing their vows, intend total fidelity, openness to life, and mature self-giving the sacrament demands. What was lacking at the beginning of their marriage has now been supplied and anything that was a barrier to valid intent, capacity and disposition has been removed, the marriage, which was presumptively valid before, is now valid in fact, and the abundant graces of the sacrament available to them.
The best use of these questions in the RCIA session is as you are doing, generating discussion, not with the outcome of everyone coming to their own conclusions, but to have an opportunity to restate the teachings in a way that applies them to the matter raised. This is how Jesus taught, when someone asked him a question, he gave a story, analogy, or example to illustrate his teaching.