How to track Assignement group modifications (Audit?)

Hi Experts,

I want to track changes done to assignment groups. So we want to give access to some managers to manage their own groups (change operators, manager name or coordinator). We want to save the different changes done to these fields in the assignment file. I had 2 ideas to do this.

1 - Audits (Not sure how to set up)

2- Activities (create a new activity table and populate it like it is done in incidents for example)

Is one of the 2 methods the way to do it? Or is there a better way? 

Thank you in helping me get the best way to appoach this requirement