If you give them safety instructions first and then don't hover too much, kids are generally OK with it all.Make sure everything works well.I think more accidents happen when tools are blunt or inadequate, I have had 7 year olds sewing and I keep an eye on tool use etc.They have to pass a licence test with me before I let them use everything.They don't mind, and understand it is for safety reasons.I give them a certificate and a bit of material when they are ready.I live in an area where there are not many kids now, and I miss having the sewing times.
PS Kids get to use these tools and power tools whilst they are in High School. In my opinion, the Science laboratory activities require closer vigilance.