Sending E-mail to subset of Organic Group

Hey Everyone,

I have an Organic Group and would only like to notify only a subset of the group about new content. The catch is that the subset of the group will (probably) change with each piece of content that is posted by the group owner. (The group owner is really the only user who will be posting content.)

I have been looking through the various contact, e-mail, og, and subscriptions modules and I am not seeing a clear way to do this. What would be ideal is while creating the node, the group owner can select which users to notify. A second possibility would be for the node to be created and then the owner selects a list of people to notify about it.

Any guidance you have would be great!