Well that should be enough then.
Food is a bit pricey there, but there are online services where you can place an order before you depart, pay with your credit card and tell them when to meet you at your boat. You fully customize like a shopping list and aren't button holed into those silly charter food packages. They work with all the charter companies.
For what you might save, I would never want to deal with the coolers and forms. Having one bag slung over your shoulder is a serious advantage when dealing with "the islands". Picking multiple heavy items in and out of cabs, on ferries, through customs, etc, sounds very cumbersome to me.
Maybe bring something you absolutely must have and can't get.
Another alternative to consider: I much prefer to inspect the food that I buy instead of having someone who doesn't care pick out the first thing they find. So we passed on pre-ordering and planned to go to RiteWay the night before. We were so wiped out from the day of travel that we didn't make it out that night, so we went out at 7am the morning of our departure. RiteWay's main location was an easy 5-minute walk from the Sunsail/Moorings facility, and we were back in plenty of time for our 9am chart briefing. We had three of us to lug the groceries back. Each of us carried 2 gallon jugs of water, and we had daypacks to put the food in. However, we did not provision heavily - we were only buying food for lunch every day (mostly cold cuts and stuff). Heavier provisioning would have probably required a cab ride.
The RiteWay store was a little higher priced than mainland supermarkets, but not by as much as we expected.
Some people don't want to do any of this shopping while on vacation, so the services are nice for them. But my wife can be picky about brand names and condition of fresh produce, so this option was much better for us.
One warning: Although RiteWay's flagship location is a nice sized store, their selection was spotty for certain food items. For instance, the deli counter was completely out of roast beef, turkey, and some other cold cuts. The only meat we could find that we liked was ham, which obviously could be a problem for some people. Some of the advance purchase services claim that by ordering ahead you avoid out-of-stock problems, but I'm not sure the laid back island people would be that diligent. I'd appreciate comments on this from those who have actually used their services.
Also, RiteWay has affiliated stores on the other islands. Selection is pretty good for small stores. Prices seemed to be a little higher on the more remote islands, but still cheaper than eating out.