Lesson Book: For each song, he should look at the diagram above the song showing which finger numbers and keys for the “position” to play the song. (He should sit with good body posture and hand posture). The music can even be just listened to and sung to before he even plays the song on the piano. This will help him internalize how the song goes.
Writing Book: The pages I assigned above are some of the simplest, yet he will need parental guidance to complete each page successfully. The instructions for each page should be fairly straight-forward.
T,TLS: This song I’m having him learn by rote since his playing of this piece will then be guided by his ‘ear’ and he can focus on keeping good hand position and using the different fingers involved in playing.
General: Regarding his daily practice, the important part is to let him taste the structure of trying to repeat tries so that he can keep up with the music (of course within the bounds of his overall attention span). Sometimes students, get a little frustrated when they make repeated mistakes but it’s ok to push them a little beyond their normal limit and then ease off with a little break. Then they can come back focused to build on what they learned in the previous session.
Sessions of just a few minutes are ok. So then he can 2-3 practice sessions per day. Regularity is more important than practicing a lot on one day and then nothing on the following days.
Lastly, if he can have a piano bench that allows the bottom of his forearms to be parallel (same plane) as the top of the piano keys. Also, if he can have his feet supported with a foot stool, he’ll feel supported. To accommodate his small size, it might take some creativity to create that situation. Sometimes, it’s ok to let his feet dangle while sitting with good posture still.