Albus, if you can get someone to cover you then do if you feel it's too much..otherwise:
Food is "festival style" sleeping in big top with no loos, and there is no where to sit and no camp beds allowed.
Festival style food means there will be choices which is a good thing.
There must be loos..it's the law!
Take a shooting stick/camp chair with you that you can carry easily or one of those haversacks that's a chair too. There is definitely a Leaders' lounge for you to have a sit down while the girls are doing instructor led activities.
Presumably the leaders aren't sharing sleeping accommodation with the girls? In which case, please your case with any guiders who will be affected as you inflate your comfy airbed. I have shared accomms with people with bad backs/joint issues before who have needed a higher bed than the tone on the kit list and no-one minded.