Restricting Authors to Activate Page

We have a use case where in we have multiple sites on the cq authoring environment. Users & Group are created to take care of the Authoring of the content, review by another group and then publish and it works fine.

For one of the site we need to do some change in the workflow wherein users in the group need to approve the content created/updated by other users of the group i.e. same user should not be able to create/update the content and publish it. It should be reviewed by other users in the group and only after approval, it will be published.

We are looking for best practices for this use case. Sample examples would be helpful