Changing notification preference for many members at once

[evcom]

Because I need to cleanup my mailing list, I plan to change the bulk mail option (allow e-mails from admin) for a majority of my members (but not all) and I wonder what is the best way to achieve this.

• Option 1
  I tried downloading the Member List where I changed the option allow_admin_email  to the required value and then re-uploading it. However, this does not seem to work as the system cannot overwrite existing members with the same member?
   
• Option 2
  Other option would be to change the option manually in the database. With about 800 members this would be quite a big job.
   
• Option 3 
  Resetting the allow_admin_option using an SQL command like: UPDATE core_members SET allow_admin_mails = '0'; - and then setting it to 1 where required (and then setting it to 1 where required)
   
• Option 4 
  Changing the setting individually in ACP (lots of work!)

Option 1 would be my preferred option as it would involve the least amount of work. Is there a way to make Option 1 work? If this is not possible, what about Option 3?
Any pointer is appreciated.

[bfarber]

You could use the REST API for this, but honestly there's not a lot of options built in for mass-updating this value because it controls user preferences for whether or not to receive marketing emails for the site and under many laws (including GDPR) you shouldn't typically be changing this for users without them explicitly requesting to do so.

[evcom]

Thanks @bfarber for your thoughts. I will have a look into the option with REST API. 
Before I change the value I will get consent from the members so it will be fully GDPR compliant. But I will have to make this call outside the IPS Application as many will not login to change their preferences.