I went on an 'all inclusive trip' to Aruba a few years ago. It was arranged local club and cost us about $2000 per couple. The fee covered room, food, and drinks. During check-in they strap on a colored bracelet that you show in the restaurants or bars. It was good all the time (in fact there was a period in the day when the bar would only serve those with a bracelet). It didn't cover the most expensive items like filet's or good bottles of wine, so you aren't charged for stuff unless its something you really want to treat yourself to. But the room was nice and the food and drinks were real good so there wasn't much that we had to pay for. The only things I ended up shelling out money for was tipping, gambling, shopping, and excursions. We had a blast and probably got our money's worth by not having to pay for the amount of alcohol we drank. I would definitely recommend you look into Aruba.
I too would avoid Nassau. I know a lot of people who have had a good time there, but I got fed up with the people asking for handouts or trying to aggressively sell you useless trinkets. I was there to have a vacation, not to get harassed.
Also check out Curacao. I have never been there, but its my parent's favorite destination in the Caribbean.