Pillow case is a good place to start. Nice long straight seams. For us "experienced sewers" we forgot how difficult it is to sew a straight line and manage the speed of the machine.
If that goes well, you might progress to large blocks and sewing them together.
I would stay away from stuffed animals. My daughter's girl scout troop when she was about 10 went to a local shop to learn to sew and the owner had them making teddy bears. They were definitely unique. Today - my daughter is 19 and when I mention to her about sewing with me (I have three machines) she trots out her bear with uneven arms and legs and says something like - "You want it to look like this!"
So remember the golden rule - KISS - Keep it Simple