OP, I wanted to add my response to your actual question about wedding etiquette.

I think you were asking about what *YOUR* responsibility is to this couple, insofar as traditional etiquette. However, etiquette refers to the expectation of social graces. You showed MORE than enough, so you shouldn't question yours.

The etiquette is lacking on the part of your son and his bride-to-be.

Hugs.

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"The errors of faith are better than the best thoughts of unbelief." - Thomas Russell