Idea: Create a memory book for parents

While we're on the subject of children and making books. You could also use the self-publishing services to collate a collection of photographs for parents.
This could be useful for:
- Photographs of a baby's birth
- Photographs taken over several years of a child's life
- Photographs you take in a special photo shoot. With this idea, try out several locations, and mix action shots with posed photographs (if the child is willing to sit still)

Book creation sites like Lulu.com offer several formats. This book is going to work better as a hardback, but this format is more expensive, so review your pricing and format according to what your clients would be prepared to pay.

For tips on how to take photographs of children, see:
Digital Photos 101
Kodak