Here's the easiest knit blanket idea ever. Obviously, you'll want to recalculate the stitch count to get this campaign's desired blanket size, but look how you can blend a whole bunch of odd skeins together to get something really attractive. And garter stitch has a wonderfully meditative quality -- you never need to stop to think of what you do next, it lies flat, and the blanket comes out extra-thick.
Reminder: the requested size for blankets for this campaign is minimum 40 by 45 inches (1 meter by 1.14 meter), maximum 50 by 50 inches (1.27 m square). At a standard worsted gauge of 5 sts/inch (20 sts/10 cm), that's 200 to 250 stitches across. Yes, you'll need a circular needle!
The same web site that posted the pattern has a number of color suggestions in another post, so if you don't trust yourself, take a look at those. But -- you can trust yourself. Trade with friends to get a good mix if your own stash doesn't excite you.
Remember: all wool -- or other animal fiber -- is best. If you can't do that, no less than 75%, please. Bear in mind that some kids may end up sleeping near an open fire, and 100% animal fiber is safest by far.
This idea appeals to me in its great simplicity. I'll post my colors tomorrow.
Edited to add:
You could also, if that blanket worked as a single piece is going to be too heavy, or too daunting, work 4 rectangles, following this idea, and then sew them together. You could even join with friends, each knitting one chunk, to make a single blanket that way (be very careful to make sure you're all knitting at the same gauge!).