Is the question one of legalities?
Critique of the plan?
There's absolutely nothing wrong with flying at night, helicopters or airplanes. You do want to be properly trained and equipped to do so, darkness presents unique challenges. Nights, too, are different, physiologically.
This charter, properly planned and prepared, is just another charter. Otherwise, it could be front page news.
Critique-
Unless the "relatively large courtyard" is a quarter mile or so on the side, do not try this landing without a pilot directable searchlight.
Visit the proposed LZ in daylight, look at size, access, security, obstacles. Keep in mind, all LZs are smaller at night.
Check legal issues and compliance methods.
Train firefighters regards helo ops. Physically brave, take charge personalities, ignorance, and helicopters are not a good combination. Really good when they know what's expected, however.
"Performers?" Get ready for time issues. If you can't arrange some flexibility on your part, expect unhappiness.
Arrange to have a tactful and competent handler to train, translate and guide.
I'm not a big fan of lighting LZs at night. Mark the bounds, as dimly as possible- think airport- they don't have a gazillion candlepower lights all over the place. Bright lights obscure obstacles on your high recon and dazzle you in the LZ.