Sounds like a usecase for
https://github.com/centrifugal/centrifugo
https://news.ycombinator.com/item?id=17798756
But the main problem with this is that the users will be non-technical and I think chat would be a bit of a confusing medium for the kind of communication we're trying to achieve.
That aside, there's something Linus once said that I love:
“If you think your users are idiots, only idiots will use it.”