Instead I have sent an email which is "Here are all the reasons why it could negatively impact on your visit, and on other visitors, the ball is however, in your court."
I'm not sure if that was actually the crueler email to send.
Because they now could do the thing they want to do, but will have to admit that they are knowingly potentially having a negative impact of the fun of others.
In other words "How much of a twunt do you want to be?"