Remember he is only nine, ……or will my 8 1/2 GS learn alot this next 6 months? Five year old has "way to go", but always keen to help ???
We have been working on a "soap box trolley", for some time and it improves every time we have a session, must be short though. If you end up machining etc they get bored. I set up ready made parts for them to "find". They always ask for a go on the morticer, only safe machine in my arsenal to my mind for a nine year old. Metal bending on the jig is always requested, with supervision of course.
Anything safe that stop youngsters wearing out their thumbs is great in my mind.
Built a oversize "tank" with the daughter once, with cd discs and wooden cross pieces, not sure how safe that was with the tensioning? Not to sure about rubber bands myself these days.
Good Luck.