[Answer]-How would I implement a change approval process for a Django model?

Check out http://viewflow.io/. This might be helpful for your use case or you can extend this to suit your needs.

I would create another table (tablename_approval) with columns something like

approved | boolean
approved_by | foreign key to user
timestamp | timestamp

to track the state of each individual row.

You might want to consider an enum rather than boolean to track the difference between items which have not yet been approved versus those that were checked and intentionally not approved.