Checkout the website icopybot DOTCOM (sorry, this site wont let me post web links yet, ha!!)
Navigate to icopybot DOTCOM / blog / share-iphone-game-data-file DOTHTM
The procedure mentioned is for iTunes Backup manager for Windows, but their latest sofware is iBackupBot for iTunes.
I can do the export bit, but become a little stuck on the restore section, as I can't find where to select restore modified files only.
Hopefully you'll have more luck than me, then you can update this post.
ps, actually as you and your wife are JB'd, maybe all you need is a something like the iPhone Browser (available at HTTP : // code DOT google DOTCOM / p / iphonebrowser / ... that should allow you to copy the necessary plist files from one device to the other.