I would also suggest simple squares for 4 patches. Nothing too small, maybe a couple 5" charm packs, one with a print and one neutral or solid.
One thought and sorry if I sound negative, but I'm thinking of 8 year olds in my family and would not let any of them sew unassisted. Of course, every child is different and she may be more mature. Is it OK with her mom that she has her own sewing machine and will sew solo?