Now that you have an idea of what your pages are going to look like, take some time to do research. Take pictures, pose your children or pose yourself. (Don’t take pictures of children without written permission from their parents). 

You can also do an internet search to find reference photos. Photographers are very serious about their photos and will sue if you steal an image directly or have an image too simular to theirs. Use several different images to come up with your illustration. You might take a nose style from a few pictures. Hair styles from another. You can piece together a person from many photos, but drawing all or part of someone else’s photograph/illustration is not a good idea.