Not sure if it's possible, but my kid was left with my Mac for an hour and managed to delete a huge amount of files. He did a lot of damage, and I'd like to repair as much of it as possible.

Leaving kids alone with computers is never a good idea. Now you will have to restore those files back, preferably by reading https://www.insanelymac.com/blog/recover-deleted-files-on-mac/ and taking some of their tips. I'm sure you'll be able to restore at least some of the files your kid deleted.