Easiest way to implement captive portal authorisation

[Dark Light]

I am creating a system for a Lan event, that gives the users a way to arrange games and add people on services like Steam. It will use a SQL database for authorisation. I am already using pfSense as a router. So my thinking is that if I combined the system with a captive portal, where there was a 10 minute timeout and where the system resends the POST information every 5 minutes, that it would force people to use the System.

So what is the easiest way to implement authorisation for a captive portal, I know the proper way would be for the system to send user information from the site to the pfSense server and then for pfSense to connect to the SQL server to validate the Authorisation.

The thing is that, since this is a Lan event and security is not an issue, I'm thinking that a simpler less secure solution might be suitable. I know you can set up pfSense to give the user access to the internet when they just press a button on the captive portal, so maybe the system could automatically send that POST if the user is authorised, or maybe some other solution.

Thanks in advance.