Child Record Change Notification

I am building a lessons learned / read across database. There is a lessons table and an actions table for action items assigning and tracking.

Here is how it will be used:

1. Person records lesson
2. Checks a box to read across the lesson to other users
3. Adds action items to an action items table that is related so that each lesson record may have many action items
4. Change notifications fire so that users selected for read across are notified of new lessons and updates to lessons

This was pretty easy to set up and is working great, but i would like to fire notifications when action items are added or updated and I can't seem to get that part going. I am trying to do it from the lessons table. Any suggestions?