You will need

Jacket
3 - 6 months (16in Chest) 2 Balls
6 - 9 months (18in Chest) 3 Balls
9 - 12 months (20in Chest) 3 Balls
12 - 18 months (22in Chest) 4 Balls
18 - 24 months (24in Chest) 4 Balls

Cardigan
3 - 6 months (16in Chest) 2 Balls
6 - 9 months (18in Chest) 2 Balls
9 - 12 months (20in Chest) 3 Balls
12 - 18 months (22in Chest) 3 Balls
18 - 24 months (24in Chest) 4 Balls

Slipover
3 - 6 months (16in Chest) 1 Ball
6 - 9 months (18in Chest) 2 Balls
9 - 12 months (20in Chest) 2 Balls
12 - 18 months (22in Chest) 2 Balls
18 - 24 months (24in Chest) 3 Balls

7mm and 8mm Needles
2 (3 : 3 : 3 : 3) Toggles for Jacket
4 (5 : 5 : 5 : 5) Buttons for Cardigan