I tested this hat for Julie. It was a very fast knit. I knit the 12-18 month size in an evening. I messed up the decreases on the first hat and I guessed confused Julie so that she'll need some more time to bring out the pattern to the rest of you.
The large size, with the knitted i-cords, needs just a bit over 100 yards of DK weight. This is a perfect use of your leftovers. It was the first time for me knitting a bonnet. It amazes me how a flat knit is shaped via decreases and goes so cutely over a little one's head. A hat without a closure does not work these days. At. All. I guess a ribbon would fit nicely here as well, but since I did not have a suitable one at hand, I just knit an i-cord.
This is a suitable last-minute gift.