The mistake that fills the last week
Reversing the order is what makes a shower stressful. Planning games before the guest list, or buying the cake before the replies, means redoing that work the moment the real number shows up. The calm version is unfashionably linear: fix the day, send the invitation, let the count build, and only then spend money and set the schedule around it.
One quiet reassurance while you work through it: My Joyfullday holds the page as a private draft until you publish, so an early, half-written invitation is never visible to a guest. Publish when the date, venue and reply button are true, keep editing the softer lines as decisions land, and the checklist runs itself down to a calm final week.