Can I really ask for black tie over WhatsApp?
Yes, when the message carries a page built for the occasion rather than trying to be the ask itself. The ceremony belongs on the page โ formal wording, full venue, dress code section. A short message handing over that page loses nothing; a long chat paragraph does.
Should older or senior guests get something different?
A phone call before the message costs nothing and says everything. For the small number of guests the occasion formally demands paper from, send paper and print the page's QR code on it โ they get the card, and the same page keeps the details correct for them.
How should the reply button sound formal?
Let the page use kindly reply by with the deadline visible, and keep the button itself plain. Guests trust a clear button; formality at the reply stage means the deadline is stated gracefully, not that tapping should feel like signing a register.
Is one message to a family group too casual for a formal wedding?
Yes, for a formal occasion. Households deserve a message with their name on it. If you want the chat for celebration rather than delivery, post there after every household has received their own note โ the group becomes the party, not the postbox.
What if a guest replies without ceremony?
Answer the yes, not the register. A guest who writes that they wouldn't miss it has accepted in their own voice, and the page recorded it where it counts. Tone belongs to the guest; correctness belongs to the list.