I think the RSS idea would be best in order to not clutter up people's email inbox's and is a great way to quickly push information to others.
In terms of being able to generate RSS Feeds based on Tags this is not a current feature from what I can tell after looking into the Blog RSS code. I don't think its a major endeavor to add that capability but it is something that would need to be coded.
You can always submit a feature request or if this is something your organization needs ASAP you can always get in touch with some of the Tiki Developers to discuss using their services to develop this feature.
Hope this helps