Your post title doesn't have anything to do with your actual post. When you make a post, please write a descriptive title for your post that has to do with why you are posting.
Have you already tried creating a group in your address book?
I don't know how to leave a voicemail to a group of people. I just experimented on my phone. You could record a voice note, and send it as either an MMS or an email to a group. I don't know if that would work for everyone or not. I have a friend that calls a bunch of his friends with a recorded message. I'll get in touch with him and see if he can tell me what he uses.