Our last two trips have been with couples who don't live in the same state we do. Here's how we handled it:
Asked each couple to menu plan two dinners and two lunches.
Then I asked them to each give me a detailed grocery list of what they needed to prepare these meals.
Two couples packed the various meats, cheeses, etc. in coolers and brought them from home.
I ordered everything else on-line from Riteway and had it delivered to the boat.
When we met up on the boat the first night, we shared receipts for what we brought with us and I shared the Riteway receipt - each couple brought a check and we settled up. Split the entire costs by 3 (3 couples).
IF a couple didn't want to plan meals, I was going to plan for them.
The only bill we didn't split 3 ways was the liquor bill since we all drank different things - that was split out by specific couple.
This has worked for us really well in the past.