Hello Clive,
Hopefully you'll be able to work from different references as Chris suggests. If you have to use the photo, I do like what Mike did, however I have recently read that the best way to create a successful portrait of two is to have them interacting with one another. In this case I think you may be able to remedy the pose by having the mother's eyes looking directly at the baby. That way they would not be competing for attention as they are now.
Good Luck.