I would imagine it would be clearing the floor (party popper crap, paper towels, food etc.), may use quite a few plastic bags.
Toilets may be a mess due to drunk people (may be 'body fluids' i.e. sick, etc), kids always mess around in toilets so they could cause a mess.
May have to clear food? more bin bags. Have they got enough space in a bin/skip or do you have to dispose of it yourselves?
I've not quoted for a clean like this but just trying to help, so I'm probably not saying anything you haven't already thought.
I'd quote slightly higher than a normal 'office' type clean to make up for the rubbish thats gonna be about. Spilt drinks and stuff like that.
If there is any 'body fluids' (it sounds gross, I know) you could charge extra due to the risk.
Hope I've helped, I've probably made you feel ill with all the talk about body fluids!