For coaching it would be nice to have folder for Races. Each race would have activity type (ride, run, tri etc). You could “subscribe” athletes for each race category A, B, C. Visually that could look like tag with athlete name. Subscription to race would automatically show up in athlete calendar.
More basic approach would be separate event for each category in same race. Then Folder would look like “Park 5k run - A”, or “Park 5k run - C”, depending what you select.
Other way to get same result (connect race with multiple athletes and it shows in calendar) could be to add race tags in Athletes View. That would need some table with races to choose from. I could be done like tags with name and date field.