We took our summer vacation very early this year, last week in fact. When we left Minnesota for Florida it was too chilly for shorts, I had to make Isaac try on his summer clothes to make sure we packed things that fit. Turns out he had plenty of shorts and shirts but had outgrown all his hats.
I used the Betz White bucket hat pattern for probably the seventh time, this time in a medium. I can't say enough good things about the pattern - it is easy, comes in a wide range of sizes, and fits well. It's a little big on him but he likes to pull it down over his eyes so it works out ok. Here's the little dude playing his first game of mini golf in his new hat.

I used Kokka Trefle vehicles, linen, and 2 layers of medium-weight fusible interfacing. I like the amount of interfacing, it keeps the brim from flopping in his eyes.