Network gurus: advice setting up public WiFi inTRAnet

Looking for advice from network gurus on this situation. My company runs a large event every year (athletic competition). Real-time information about the event is published on a website. However, our one wireless access point isn’t really up to the number of people in the event venue who want to look at the info on their smartphones, and our ISP certainly isn’t up to it.

What I’d like to do is set up a public intranet with a server to provide the info without burdening our Internet connection. We probably need to support 400-500 WiFi users at a time. Data volume will be pretty low – no large images, no video or audio streaming. And since no Internet access is required, no super-fancy firewall features are needed either.

I’m competent enough with computer equipment that I can probably get the pieces set up to talk to each other. The problem is knowing which pieces I need. For example, I don’t know if a WiFi range extender would enable more clients to connect, or merely enable the same number of connections from further away.

Any suggestions would be much appreciated…