I just looked up this property and now the Cayman Islands are definitely on my list of places to visit. That property looks GORGEOUS.
With that said, a $70/night resort fee is just a rip-off. Following this thread to see if anyone has success getting the resort fee waived. I'm not big on being all DYKWIA, but this seems a case where bringing up Platinum status or escalating to IHG corporate might be the way to go.