If we travel with more than just us we have a purser who takes care of the money. The initial provisioning is split at the beginning then with 4 of us (2 couples) each couple puts $400 into the kitty. This is for mooring, ice, reprovisioning along the way. Sometimes we need to kick in another $100 per couple, sometimes we just use the excess for the last dinner out or taxi fare to the airport or ferry. Dinners out can be tricky with that many people. Decide in advance if you want separate tabs and make sure at the beginning of the meal that your server can do that.
We recently traveled with 4 couples. 3 couples were pretty good drinkers, I do not drink and my hubby has an occasional beer. Realizing this they were all gracious enough to adjust the tab when it was on one check. Be up front about expectations and be prepared to implement plan B
It is better to be happy than it is to be right