for my 7yr old nephew and 4 year old niece I had them pick out fabric they wanted and "measure" how much they needed to fit on a pillow form.
Then I sat at the machine and had them stand and operate the foot control (with the speed low) saying "go" "stop". Was the perfect level for them for a first project. Then we made puppets the same way, and once they were sewed they colored the puppet faces with fabric markers. They were supposed to color the whole puppet but they decided they wanted to cut and sew clothes, a hat and hair, I used the needle to put yarn on for hair but had them tie the knots and cut it the length they wanted.