“He is our son” is absolutely not the justification for the scenario I painted. The justification, which is indeed a mandate is the Church’s teaching that the homosexual must be treated with dignity. If one movement was made betraying their sinful relationship, the family would have to ask them to leave. As long as there is a “don’t flaunt, don’t mention” rule which is obeyed, their presence alone could be acceptable. Tough situation.
If children weren’t involved I could go along with you. I would say that either man should be welcomed individually but not together as long as children are present.
Of course, people involved in destructive behavior should always be treated with dignity. This is a tough situation with some hard choices with serious pitfalls for the parents who face it.