I followed the third size (18 mo) as indicated in pattern; but found that the result seemed too long for the width. I therefore changed the bottom band to be just rows of double and single crochet; keeping the collar and button/buttonhole bands the same. I made a small bucket hat (using 7 granny squares around hat) and decreasing at top gradually to about 10 stitches which were sewn together. Brim was made by a foundation row of single
crochet around the bottom of the granny square circle; followed by double crochet rows to reach desired width. For the final row do 3 double crochets alt with 1st double crochet around rim; fasten off; work in ends.

The next time I make this I will use same yarn and hook, but make the smallest size and see if this drapes and sizes better.