iPad 1 apps keep crashing
Have him sign out of the App Store in settings, then sign in again, then purchase a free app.

This resets the digital certificate that tells the device it can run apps for that account. Often these certs expire if you don't download anything for a year or more and renewing them happens when you request a new app.

When this is done, also check on iCloud backups and enable them if you can. An ounce of prevention, etc....