I begged for a year before I got to start sewing classes at 8. Even then I was "too young" but the lady who was teaching the class made an agreement with me. If I promised to pay attention and do every task and assignment, she would allow me to participate. My first project was a sleeveless dress, with a set in zipper. I learned how to place the pattern on the grain (and WHY!) why you follow directions, and I learned just how much fun a seam ripper is when you don't!
My Grandmother (who raised my sister and I) just could never get over the whole "fear factor" so she was never able to work with me and the sewing machine. That didn't stop me, I loved sewing and all hand crafts! I learned to crochet with thread at 7. My Great GrandMother was a firm believer in Doing is Learning. She gave me hook, thread and a sample bit of lace to "read". I made enough lace to put on a pillowcase (remember THOSE days?). GGM had an OLD Singer, will all the fun feet that were ever made for it. It was a special day in my world when I was allowed to use her machine to finish a project!
I would suggest that you assess the interest level of the child, start with big dull needles, burlap or plastic canvas is good and if the interest stays, nothing wrong with learning the rules and best practices around the machinery! Good luck and have fun. Making lasting memories is the best part.