I believe God can bestow grace upon a couple even at a wedding ceremony or at any time our hearts are fixed on seeking His blessing and approval.
Grace is free unmerited favor.
The Lord says that he gives the rain to fall upon the just and the unjust.
He gives the sun to shine upon the just and the unjust alike.
We don't deserve the sun or the rain, but only the wrath of God. But God in his mercy and grace gives us what we don't deserve. That is grace. Both the saved and the unsaved receive the grace of God.
The grace of God in salvation is available to all. Christ died for all. But the effects of that grace can only be appropriated by faith. If someone does something for me, even though I don't deserve it, and I refuse to take advantage of what he has done, then I am a fool. All those who refuse to take advantage of the grace of God provided through the atoning work of Christ are fools and eternally damned. His sacrifice must be appropriated by faith and faith alone. There is no work that can ever appropriate the grace of God.
God's grace does not come through baptism. Baptism is a work. It does nothing special for you. It does not save you. It does not make you any holier. It only makes you wet. It is done by a believer after salvation in obedience to the command of Christ. That is all.
Grace cannot come through works like baptism. That changes the meaning of grace.
Again understand the meaning of grace through Scripture.
Romans 11:6 And if by grace, then is it no more of works: otherwise grace is no more grace. But if it be of works, then is it no more grace: otherwise work is no more work.
--It is either grace or works. It cannot be both. The RCC has chosen works. Salvation is through grace, not of works.