You will need a set of size US 6 (4.0 mm) double pointed needles for the booties.

Finished measurements:
Hat and Booties - to fit average child for the size worked.
Blanket - 29.5” x 39.5” (75 cm x 100 cm)

Yarn used:
Hayfield Baby Bonus Spots DK
Shade 203 Playdate
Booties - 1 ball for all sizes
Hat - 1 ball for all sizes
Blanket - 4 balls