I started sewing pretty young via my Mama's ancient black iron post WW2 White sewing machine. Never had an incident or accident on it. Fast forward 30-40 years and I sewed through my finger on my beloved Bernina while staying up way to late to finish a costuming job. Mayor Munchkin's coat was a booger to make & I was tired. Ended up with broken needle parts in my left pointer finger - required a tetanus shot just to be safe & made everyone at the Dr's office cringe.
Anyway - my point is my accident happened because I was tired & got careless. A supervised child should be fine.
Good Luck!
Donna Mc