We've been on the Moorings 5800. If you were on that or a similar boat, I think one boat would be fine. There is plenty of space to spread out and there was a lot of storage for food, although I am sure you'd need to re-provision during the trip. The challenge with that many is the food - I'd see if you can find one willing to handle the majority of it and put together a shopping list. My wife always does it for our trips based on feedback from the group, typically planning out dinners/lunches ahead of time.