Ag-Grid: Implement button to get child count

I am demoing the latest Ag-Grid Enterprise and I have implemented the Server Side Row Model successfully, including the ability to send back group child counts such that the grid can display child counts for groups.

However, displaying child counts for every group is incredibly time-consuming for my database to calculate and so not a good default. However, I would like to add a “Count” button or similar next to each group such that then when clicked it will send off enough information to my server side implementation that the child count can be calculated and relayed back.

I can imagine how many aspects of this could work, but primarily I need help understanding how a button could best know the groups it is under (the DOM isn’t exactly laid out in the same nesting structure as the grid itself so getting that information that way doesn’t seem entirely straightforward).

Thanks for your time!