We do something similar to this for topics that require people to confirm they have taken an action. The basic idea is to create a list of user names in the topic that are prepended with a :white_large_square: , and then ask users to edit the :white_large_square: icon to a :white_check_mark: when they have taken the action. It works because people get a notification when their username is added to the list. If someone fails to respond, they can be reminded to do so.