A party scattered across four places
Planning normally happens in fragments. The date lives in a calendar, the guest list in a spreadsheet a cousin technically owns, the venue negotiation in its own thread, and the final invitation in a message you will retype once everything is set. Each fragment is manageable; the joins between them are where evenings disappear, because every join is a copy-paste someone has to do and then check.
The alternative is not a project tool. It is a single thread that holds the structure: one conversation with Jitabi where details get sent, changed, and turned into an invitation page. The chat is where planning happens; the page and the list are what the chat produces.