Kids and Linux/Opensource , all my kids use Arch Linux ( 8yrs, 12yrs and 16yrs)
my 8 yr old likes using GIMP , my 12 yr old daughter uses Krita - was interviewed earlier in teh year https://krita.org/en/item/interview-with-dolly/
My eldest has a youtube channel and uses kdenlive to edit his videos.
they all prefer their home PC's Operating System and software over using the Windows PC's they use at school
I hope they continue to use and enjoy.
You should post the image of the pokemon that he colored in GIMP :). Talented 8 year old...
I have no kids (by choice) but yeah if I had one - I would hope he / she would use / prefer Arch Linux over Microsoft products too... but once they would be old enough I would let them choose. You gave them a choice and knowledge - that's awesome. All you can do now is support them in their choices and hope.