I doubt there is enough bandwidth available to be sending multiple video streams from the controller. At least with any sort of decent quality. Telemetry data barely consumes any bandwidth compared to video, so I can see that streaming to multiple devices easily.
I think the HDMI out on the controller is probably best to allow others to view. From there, you can do whatever you want with the HDMI signal. Feed it to a 2nd tv/monitor, feed it to a laptop acting as a hotspot for others to connect to, stream it to youtube (via the laptop, assuming an internet connection), etc.