Could work: a combination of wired connections, asking attendees to bring their own 3G dongles and providing a local cell base station for areas with poor mobil

Could work: a combination of wired connections, asking attendees to bring their own 3G dongles and providing a local cell base station for areas with poor mobile coverage. For people with ethernet ports, you could spread a few wifi routers with wired ports, so wifi traffic is carried over to the fewer routers than to each individual client.