This app was mentioned in 5 comments, with an average of 1.00 upvote
Universum is good. Simple and easy to use. You can add photos, drawings, task reminders, track your mood, and stuff like that. It also has a password option for privacy. You can make a local backup or choose the cloud option for Google drive, or export to PDF.
Universum Diary app might work for him. You can write in a diary format, include pictures, and there is a "tasks" option that you can use to create reminders with notifications. It also allows you to backup everything to either Drive or a PDF.