Not everyone needs an account to join a game. A player can bring one or more guests to a planned game that they’re attending as long as there’s space.
If the people they want to bring along to the game don’t have an account, they can bring them as a plus one, either named or unnamed.
If you have folks who like keeping track of their gaming history, they can log a play from a planned game in as few as three taps if they don’t care to enter scores; most of the details will be pre-filled based on the info entered when planning the game.
Your attendees can become friends through the app, which would let them see each other’s collections, easily invite each other to future games at or outside of the convention, and see what sorts of games they play.
…and so much more!