How Do I Help a Widow Transfer Dead Husband’s iCloud Account?

The widow of my dead friend has his iCloud password to access his account to see photos (for example) but wants to move all his content to her iCloud account. She has inherited his MacBookPro, iPad and iPhone and can unlock all devices but does not want to loose any data when she changes administrator passwords.
Obviously she could continue to log in to his iCloud account, but would rather move all content to her own iCloud account.
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Rod Lewis