Create content approved by several users chosen by author


I would like to add the following functionality (drupal 7) :

1) A user creates a content

2) He chooses several “approval users” for this content

3) Each “approval user” receives an email and shall approve / refuse the content

4) When all users have approved, the content is published and the list of approval users is displayed on the content

What’s the best way to achieve this ? Workflow module ? organic group ? rules ? others ?


Drupal version: