Let me say up front that I own three weeks at Divi so I am biased. That said, I think you will want some "down days" after the excursions you have planned. Despite all the opinions above favoring Simpson Bay, and while I haven't actually stayed in the area, it strikes me personally as a very busy area: lots of traffic and people. For my down days, I really love the quiet of Divi, and Little Bay beach is one of the nicest on the island. It is true you will be closer to your excursion departure points staying in Simpson Bay, but Divi is only 15 minutes away from Simpson Bay. And I agree with the others that A/I on SXM is limiting due to all the wonderful restaurants around the island. I would FOR SURE not do A/I at Divi because the food there just isn't that good.

My two cents' worth.