My Photo Stream is hard to re-populate ... I think you can do it by opening a Camera Roll photo, then re-save the photo (thus making a duplicate in Camera Roll and putting a new copy in My Photo Stream). A pain to do for sure.
It would be easier then to create a Shared Photo Stream, then from the other 5s save the photos in that stream locally. A Shared Photo Stream doesn't have to be shared with anyone, just set it up for sharing and the other 5s should see the photos if they're sharing the same iCloud ID.