Shared Photostream and IPad 1 (first generation) I want to shared some photos stored on my Mac to my wife's IPad (the old one, 1st generation).

I have created a Shared PhotoStream album. My wife correctly received the invitation/notification. 

She could open this shared photos on her iPhone 4 (iOS6) but it's seems not working on her iPad (1st gen / iOS5).

How can I make it work?
Short Answer: You can't

Shared PhotoStream is a feature of iOS 6 and therefore not available on iOS 5. Some users claim they had gotten the feature working and enabled by removing and re-adding the iCloud account, however I have never seen it work.

From the official description of a shared PhotoStream (Bold by me):


  Select photos directly from the Photos app in iOS 6, iPhoto or Aperture on a Mac