Teach him to keep his fingers away from the needle. Then give him some scraps and let him go. My gkids all sew. They make little pillows. I save all my fabric trimmings and they use them for stuffing. Maybe the seams arent perfect, lots of raw edges, etc. but the creativity is there, and you can GENTLY offer advice and assistance along the way. Pushing for perfection will only push them away. I buy fleece remnants at joannes for them, as well. This fabric is very forgivingof variable seam allowances. Big squares sewn together and fringed can make grandpa a lap blanket he will cherish. Don't forget the label. Marking pens on muslin is a good medium for this task.
Good luck, and happy stitching fromm a gran of 8.