Find My 'Play Sound' notifications history
I have an iCloud Family plan setup. Most of the devices are associated with my account, except for the kids and wife who all have their own iPhone or iPad. As a test, I just signed into my kids iCloud account. I was able to "Find My" iPhone that's next to me from my kid's account. So I guess there isn't a real way to see who did it, as nothing really told me which account sent the request.
If you think it's a child that is doing it, remove the app from their device, or use a configuration file to restrict the app from the device.
Good luck!