Knitting question

Okay...for all you experienced knitters, here's the situation:

I started out this morning with the idea of making a scarf with all my
scrap yarn balls.
Circular needles: size 6 x 16" long
Cast on: 60 stitches

I'm about 3-4" into this and it's looking like it would make a really
cute little hat with a rolled brim.
Now for the questions: When would I start decreasing to make a hat for a
small child? Is there anyone experienced enough to know the ratio of
decrease per row until the end? Or would it be wiser to just create a
tube, then stitch together the end in a "+" formation?

Thanks,
Jenn
--
Two things fill the mind with ever new and increasing wonder and awe -
the starry heavens above me and the moral law within me. - Immanuel Kant