Is there a way to send an announcement to the members of the forum?
Sending a pm does work but requires the member to log in and access their inbox to read it. If going that route, is it possible to include the message in the sent email? Similar to forum post reply emails.
Thanks.. 
There is no current option to include the message in the PM email although such a change can be considered. And no plugins that send emails as such either.
If all your site members have access to the forum then there are WP plugins available that can send emails out to all of them – or is that not the case here?