Persistent group chat or some other form of reliable 2-way communication with a group
Not sure is this would work for you, but id say to try and make your own steam community group https://support.steampowered.com/kb_article.php?ref=2092-QLZX-8453#create and then use the chat function in there.
Also, is suggest making it private/invite only if you JUST want your friends. I havent tested the persistence of this, but i know the chatroom will always be available...