If you get something with Windows, it might be good to get 2+ of the same model a release generation or so behind and set them up identically before delivery. When one stops working for whatever reason, he can use the other(s) until you next make it over to fix it.

In 5-7 years, a daily driver tablet battery would probably die and need replacement. A popular tablet like iPad and some Samsung Tabs would be easier for a local electronic repair shop to source parts and put in new battery. Same if the screen breaks.