One possible approach is to use the HEART framework
Explaining some of the metrics
Why did you choose number of visits from social channels chosen as a key engagement metric?
People often like to showcase interesting and worthwhile experiences on social media, which can indicate that they enjoyed the experience. One metric that could be used to measure the impact of these social media shares is the number of visits to the event or experience from social channels.
Why specifically number of visits from social channels and not the number of shares?
It is important to note that not all social media shares are equal, and the number of followers an account has can influence the reach and impact of a share. For example, a share from an account with 10,000 followers may have a greater impact than a share from an account with 1,000 followers. As a result, it may be necessary to consider the number of followers an account has when evaluating the impact of social media shares on event attendance.