How can I provide registers to each of my coaches without giving them full administrator access?

You can add coaches/instructors to your Participant site, and then assign these to the relevant event.

After setting up your sessions (please see separate user guide here), you can assign your coaches using "batch edit sessions"

You can assign the relevant coach(es) or instructor(s).  Following this, please click "Save."

In the instructors list, you will be able to access the coaches' register.  You will find a unique URL for each coach, which you can provide to them.

Within this link, your coach(es) will be able to access their list of registrations.  They can check participants in and out, and download an attendance log to Excel if they wish.