(Also check out today's fantastic Free and Reduced Apps!)
Tayasui Sketches is an elegant drawing app for older children (and certainly adults too). I couldn't draw a sketch or a cartoon to save myself, but this app makes me want to try, the interface is so zen-like! From the people who made Drawing with Carl (which if you don't have, you should, it's hilarious fun), this one is for making more sophisticated lines. The brushes are vividly realistic, and there is no lagtime when you're drawing. Simply beautiful.
There is a pro version available for $1.99, but the free version has more than enough brushes and options available to make it absolutely worth recommending!