Laetitia,
Thank you very much for sharing this video. You are now on the stage of developing the independence of each finger.
As you noticed during working on the 5 fingers exercise, the 1-2 - 3 fingers - thumb - index and third - are stronger in each hand. 4 and 5 are weak.
I suggest you to fix your wrist first. If you keep the wrist upper, the weight of your entire hand will work for you - not against you.
Second. Do not play fast. You are playing fast because 2 weak fingers don't want to work as hard as 3 strong.
For the same exact reason you play sol 2 times.
Focus on playing slower, please. Make you 4th and 5th work by lifting them one after another
Stop on fifth and do not repeat it. Go back.
Play 2-3 times to develop the independence more thoroughly.
Thank you very much for this video.
You son really drawn towards piano playing. You are setting him a wonderful example!
I would suggest to establish the rule in your home and follow it: for the sake of the harmony one person play - another listens. Unless in future you will learn duets.