You will need

0-6 months (16in Chest) - 2 Balls
6-12 months (18in Chest) - 3 Balls
2-3 years (20/22in Chest) - 3 Balls
4-5 years (24in Chest) - 3 Balls
6-7 years (26in Chest0 - 4 Balls

2.75mm and 3.25mm Needles
3 Buttons