I love knitting for kids because projects for kids usually go quicker than others. Plus, if you're a really fast knitter, you might get lucky and see them wear the thing you've knit at least twice before it's too short, too tight, or so full of smudges and whatnot that they can't wear it anymore.
Enter the Drive-Thru sweater.
Also known as the "Quicko-Cheapo," and sized two thru 16, this cardigan/pullover pattern is quick because it calls for a worsted weight yarn that knits up so speedily that once you're done, you'll want to cast on for another one, right away. And the great thing about this is that, although there are a few color changes, there isn't a particular technique involved. In fact, even though the yoke pattern looks a bit like Fair Isle, it really isn't. It's just a couple of colors mixed on one row, then a few plain-colored rows that follow.
Better, if you don't want to work this in wool, you can use a worsted weight cotton. Shoot, you can even find some yarn for the main color, then work the yoke portion with odd-ball yarn from your stash. There aren't any rules here, except to have fun.