Hey Tiwana, welcome to the forum! I couldn’t agree with Deacon and Sharon more. It’s been my experience that you teach guests how to treat you and your space, and that all starts with the initial correspondence. More often than not, when a guest asks for discounts, favors, exceptions to your rules, or other such contingencies, it is a huge red flag. As Deacon and Sharon both explained, this usually ends poorly the day of. Guests like this tend to follow the “give them an inch, they take a mile” universal law, so you will likely have a mess on your hands in some way, shape or form. Not to mention the fact that you got less than what you deserved to begin with.
You, your space, your time and your business as a whole are valuable, and it is up to you to dictate that. Not only that, but you run a business, not a charity or non-profit. Do what you feel is best for your business, but instead of removing the discount, I’d remove the guest if it were me.