Etiquette for: If you cancel or postpone the wedding
Return the engagement ring to the giver
Send back all the gifts with a brief explanation why it was canceled.
It’s written that if a gift is engraved or personalized, you don’t have to return it.
You should inform out-of-town guests first so that they can change or cancel their travel and lodging arrangements.
If you’re postponing your wedding, of course every guest has to be contacted. Etiquette pros say that you have to send another invitation with the new date.