Ds is learning to sew on my machine (super slow setting), and he is about to turn 3 (in 2 days!).
If he messes up, I can do the seam ripping for him, there is a lot he can do himself that doesnt involve pointy things.
He has been sewing buttons and sewing cardobard shapes with holes punched in it, strining buttons onto thread w/small needle, cutting fabric with small metal sewing sissors for a year now. When he has anything sharp, he must stay sitting down and not goof around, otherwise its put away until he is in a mood to do it safely
ETA: I teach the kids sewing classes at JoAnn's, and many the 8-14yr olds have a hard time figuring out how to use the seam ripper, and they poke themselves with pins all the time!