Jackie22,
if your travelling with 3 or more others, a really fun afternoon is to contact Alfonse. Charter him for thee afternoon(split the cost) from noon or a little after. Have him take you to Caye Caulker take him to lunch with you at Rasta Pasta, shop around, then make a snorkel stop or two on the way back to AC. Try to time a stop at Hol Chan for the last hour of sunlight - if conditions are right it will be breathtaking.
Alfonse is easy(to work with) tell him what you want to do...no problem.
We did a lot of "stuff" on our last visit for two weeks but that afternoon was the highlight of our last trip - and still time to hit the hot spots at night.
You will have a blast with Alfonse!