I own a restaurant with play area. We do not allow people to bring their own food. Many reasons including allergies, food poisoning etc and also there is a restaurant so we cater for all food requirements. We do have parties and allow people to bring birthday cakes only, but they are cut and wrapped by us and not eaten on the premises.
We have more and more people bringing their own food especially for unofficial parties etc. Many even leave the wrappers for us to clear, plus mash it into the carpets etc. We recently even had a parent cracking peanuts who was shocked when we told them that it wasn’t allowed (we don’t sell food containing nuts).
Would you find it an unreasonable request to be asked not to eat outside food in a place that has a restaurant?
Also if you held an unofficial party would you find it unreasonable to be charged to have your cake cut and wrapped for you?