You can automatically assign labels by using filters here is a previous question:
https://webapps.stackexchange.com/questions/14505/automatic-labels-in-gmail

Also Here is the direct link to the gmail help page: https://support.google.com/mail/answer/6579?hl=en

I would however advise creating a mailing list using google groups for communicating with multiple users like you want to. You can find out more about Google groups [here](https://groups.google.com/forum/#!overview)