First things first, hello you there, my dear reader! I hope you're having a good day.

TL;DR How would you design an improvised adventure for a quickstart with a setting based on the character created by the players, provided a goal is to show character creation at the table? What specific tools do they need?

I'm looking at specific tools you found useful for GMing demo sessions at conventions. I've been GMing for conventions quite a bit in recent years, and I'm aware of how stressful and mentally draining it is, so I'd like to add things specifically tied to reduce the mental loadout of the poor GMs out there.

That said, my current version of the quickstart of my game (Land made of Wonder) is designed to have a setting that ties down almost all their elements to the characters at the table, so it's very difficult to provide to the GMs a content of their own for them to run. NPCs and places are "metaphors of the character's bad/good memories" and I'm skeptical about including pre-gens because I would like character creation to be a tool shown during a demo to portray how fast and "unobtrusive" it is (20 min). I'm at a loss.

I thought it could be an idea to provide a generic scheme (such as "create an enemy metaphor based on character 1, create an ally metaphor based on character 2, create a location-based on character 3, create...) and a flowchart of possible obstacles to fall to as a safety net, similar to the way Mouseguard is supposed to be prepared (Adam Koebel: https://www.youtube.com/watch?v=cRnwPu_xyb0 ) and a generic time-table of the flow of play if things go well... but maybe it wouldn't work? An alternative may be to provide characters... "half done", with some memories already built-in, let the players end character creation collectively, then have a pre-built in enemy/ally/setting pre-built on the specifics of the memories already provided, but keeping them half-open for specifically fitting memories created by the players at the table.

I'm looking for suggestions here, guys. What would you do?