Tilda fabrics, appropriately named "Sweetheart" is perfect for this one.
Cottage Garden variegated threads - it's like colouring in! They work so well and give a beautiful shaded look, especially with satin stitch.
P.S. This is our granddaughter Pippa. It was Sean's 7th birthday party, and she loved the cup cake birthday cake, with green icing, because Minecraft is all the rage and that was the party theme.
Pippa, however, had fun playing with the icing - just like playdough!