Hi I'm recently back from the excellent Eagles tour to the Oetztal and having been put in charge of the group kitty used a good app called 'tricount' to help keep track of the groups spend. I used it on android, but its also available for apple.
It allows you to set up members in the group, then quickly set how much and for whom each expenditure was for, so making it easier to allow for those joining /leaving the tour at different times or with different travel methods/beer requirements! etc.This also makes it a easier to use credit cards used rather than always using a joint cash pot.
The app will then calculate who should pay what to whom to even the spend at the end of the tour.
One tip for trip deposits paid up front, is that these can be set as an expense from one member of the team to just the leader.
I'd recommend keeping track on a piece of paper as backup tho' if you want to cross check the accounts, and/or when your hut doesn't have easily available plugs to recharge you phone!.
There's a website at www.tricount.com
(There's other similar apps available but this one certainly was easy to use).
Peter.