I think that it would be nice if people that are not familiar with these channels (and maybe even not with the underlying technology) could have the possibility to join them for the purpose of the event – synchronous communication makes sense for time-bounded events with social we’re-doing-it-together components.
Maybe just a web link suffices for that (could you give me the URL(s) to include then?), or maybe a blurb on how to connect, on the webpage or as a separate document.
(I’m fine with using the usual channels if the regulars are ok with it.)