16" circs are good for sweater necks and sleeves. I agree that for a tiny hat, though, two circs or magic loop is the way to go if you don't want to use dpns. Iven if you start with a 12 inch circ, you'll still have to switch to something else when the circumference gets too small for those.
Don't give up on circ, though. Once you have the right size, it is a real pleasure to knit round and round. No seam at the end, either.