How do I save data from old 2 old iPhones then transfer data from one to the other?
iTunes can back up everything except for data that came from a computer.

That means apps not authorized on your iTunes, music from a computer and pictures not taken on the device (stored in the camera roll) are not backed up. Assuming you don't need to recover that information, just back up the devices and archive the iTunes backup folders so you can re-load those backups on another comparable device from a PC or a Mac.

Read up on the details here:


iPhone and iPod touch: About backups


Once you've got a sure backup (I'd get a loaner phone from a friend to check the restore to see that you are happy before erasing any of the devices), you can then restore the "wife" backup onto the "mom" phone.