If the large all-inclusives of places like Cancun and Peurto Vallarta are what really appeals to you and your friends, you may find that you are disappointed in San Pedro.
However, if you are willing to experience a new adventure in a great little town that is more quaint, then you shall have a wonderful time. And if you are open and willing to try this new experience, I'd be willing to wager that you'll not be going back to doing all inclusives.
You should consider the whole of San Pedro and Ambergris Caye as your "all inclusive". Of course, you can't get away with just a bracelet or beads and will have to carry cash and/or credit cards.