If you'd like to send a CoachAccountable item (Actions, Metrics, Worksheets, Messages, Files, Session Notes) to multiple clients at once, simply place those clients in a Group.
In fact, it's a good idea to have an "admin-only" Group whose sole purpose is to deliver items in bulk. Disable clients from viewing and participating in the Group by going to the Participation tab of that Group's Settings and unchecking "Enable clients to view and participate in this group".
This prevents clients from knowing they are in the Group and makes the Group solely for your use in distributing items to multiple clients at once.
From here, click the plus sign next to Group Stream to assign an item to all or some of the members in the Group. You can even use this method to create Appointments for multiple clients at once.