You better hurry OP if you tickets are already issued and you want to try and find a lower fare on AC! As an Elite I, if you have ecredits to spare in 2013, i'd buy a latitude fare for your child and wife and then upgrade them both, purchasing the Z/D class for you

This way you get the child discount. A quick look shows the Z fare is the same as the B. Of course, you need R class, but if there is Z sometimes that automatically means there is R class too