If you need help with and IRC channel let me know. I would recommend QuakeNet as a net work as their channel services are top notch and It's dead easy to run a channel there. I'm on QuakeNet alot as well as I run other things on there so if you needed and active moderator I wouldn't mind chipping in.
An IRC channel is the proper implementation for this. Trying to use a messenger is only going to be messy. As others have said the channel only needs to be open on race weekends, It can be locked with a password when it's not being used so it doesn't require 24/7 moderation.