@Amanda982 How violating that would feel. Ugh.
As for the review, I would absolutely mention it, but also mention he was a good guest otherwise. Something like:
“X was a friendly guest and left the space clean. I did learn after the fact that he allowed two other unregistered guests to stay in my home.”
Just state the facts so other hosts are aware what happened.
As for charging for the extra guests I would do it. You don’t have to contact Airbnb. Just request the funds through the Resolution Center. Explain politely there is an extra charge for extra guests (as long as this is disclosed in your listing). He admitted to the guests and the extra cost is minor so hopefully he won’t object.