That data for facial recognition and other photo metadata is stored in his user folder, in App Data >> local >> google. Inside there he'll see folders "Picasa" and "Picasa Albums". If he backs those up, all of the photos and other data will be saved. He might have to uncheck the "hide folders" setting in Windows to see these folders, though.
ScotlandCalling in the chatroom says that an easy way to find the App Data folder is to click start >> run >> type "%APPDATA%" which will open that folder.
This article shows how to save faces in Picasa: http://picasatutorials.com/2011/01/saving-faces-when-you-re-install-picasa/