Have you read Divrey Torah by The Sofer Sta”m Rabbi Steve Bar Yakov on Mezuzot and Tefillin?
You can read them at:
There you can read an introduction to the Perashiot portions written in mezuzot and Tefillin including subjects like the Unity of G-d, accepting the yoke of heaven, a land of milk and honey and more.
I also make Tefillin especially for your grandson or son. Those who purchase Tefillin can participate via video chat in the workshop I call Tefillin – The Spirit of Bar Mitzvah