This is the whole difficulty. The facts take four lines; the tone takes the rest of the card, and the failure mode is always the same — a couple writes the news as a confession, and every reader obligingly treats it as one. Five rules, and they hold for all six examples.
Lead with the fact, not the reason. “We’re married” first, in the largest words on the card. Any explanation, if you want one at all, goes underneath and takes one sentence. A card that opens by explaining itself has already conceded that it needs to.
Say that you chose it. One verb does this — chose, wanted, decided— and it moves the day from something that happened to you to something you wanted. Compare “we ended up at the courthouse” with “we chose a Thursday and no audience”. Same wedding, two different pieces of news.
Be specific about the day. The cliff, the ranger, the grandmother on a video call. Detail is generous: it puts the reader in a room they were not in. Vagueness reads as embarrassment, and a card that will not say where the wedding was invites people to wonder why.
Never explain the guest list, and never apologise for it. No we’re sorry you couldn’t be there, no we would have loved to have you there. An announcement has no guest list to account for — it goes to everyone — so a line of regret invents one and puts the reader on the wrong side of it. Delete both sentences and nothing is missing: a marriage, a date, a place, and the fact that you wanted this person to hear it.
Give them something to do, or say there is nothing. A party, a date to hold, photographs to come, a hug the next time you meet. And if there is genuinely nothing, write that line too: “there is nothing to reply to” is a kindness, because it stops a reader wondering whether they owe you an answer or a gift. On the gift question, the etiquette is the same as on an invitation — you do not raise it, and digital wedding invitation etiquette covers why.