Hat for a two year old?

[sharmelon.livejournal.com]

I'm making a hat as a gift for my boyfriend's adorable little niece. She's about 2 1/2 years old.. but I havne't seen her in a while, so I'm having trouble guessing what the diameter and length of the hat should be. Not sure yet if I'm going to knit or crochet it; but anyhoo - to those in the know, or to those with kids this age, generally how big should I make the hat?

Thanks a bunch. :)

Oh, and I'm using Red Heart Baby Clouds, so the hat will be somewhat stretchy if I do my stitches loosely. :)