Invites and replies are the last stage, deliberately
Notice invitations come fifth. Sending early and updating by apology is what makes hosts feel like couriers. Once the date, place, theme, food, and list are real, one shareable invitation page carries all of it at once: the schedule, the address, the no-children sentence, the registry note, and the gift list.
My Joyfullday baby shower pages are built for exactly this shape: a warm invitation up front, a reply button that records each guest against the list, plus-ones inside whatever you allowed, and reminders you can send to the quiet ones a week before. The co-hosts can all see the same live list at their own access level, which means the answer to 'did you think Sofie was coming?' is a lookup, not a hunt through three group threads.