If you need to update more than one baby, you need 1 disc per baby and do it one at a time. Don´t try to update more than one at the same time. This time anyone can make the update and the family list won´t be lost.
After making the update, rez your baby again for him to load the personality.
Don´t try to update unborn babies or they will be lost or update from other version other than a 3.x baby.
If you feel uncomfortable with this update progress you will be able to get the latest patched version from any recovery station.