iPrintAnimals allows you to carry with you more than 40 drawings of animals and print them anywhere you need (which has AirPrint supported printer).
The quickest way to print animals drawings for your kids, and its with you all the time on your iPhone/iPod/iPad.
Just select an image and print - as simple as that.
The drawing will cover a full A4 page, so your kid will have much to paint.
Enjoy (the quiet when your kids paint :))