Shared Album Photos to Camera Roll

I would like to purchase a new iPad for my wife and install some 8,000 pictures on her camera roll. I know how to create a shared album for these pictures and activate the shared album on the new iPad. There may well come a time when I no longer have iCloud and would like to be assured that the mentioned pictures stay on her iPad permanently--in other words in her iPad camera roll. My wife is even less computer savvy than I am. Looking for a simple answer to a simple question. How can I transfer the pictures in the Shared Albums from me to her iPad to her Camera Roll? Or is there a better way? Once I and my iCloud account are gone I would like her to retain these pictures.