I can only assume that this is what Colin meant to put for #3...
3. Or use ClearPass with an external Authentication source. This won't use Guest Licensing.
So, if you can query your external DB (Postgres, MySQL, MSSQL, or Oracle 11g) for the ticket number or room information, then you could use that as the authentication source.
Example:
Last Name:______________
Ticket/Room Number:______________
Last name can be used as the username and Ticket/Room Number could be the password, assuming you have access to the database with that information, and it is one of the database types listed above.