You will need

0-6months (16in Chest) - 2 x 50gm Balls
6-12 months (18in Chest) - 2 x 50gm Balls
1-2 years (20in Chest) - 3 x 50gm Balls
2-3 years (22in Chest) - 3 x 50gm Balls
4-5 years (24in Chest) - 4 x 50gm Balls
6-7 years (26in Chest) - 5 x 50gm Balls

2.75mm and 3.25mm Needles
3 Buttons