You might want to switch your dates. That is when I am bringing the entire family (in laws) We will be the big group with several units and the children that will be loud and fussy and out of control. We will be there the 1st week of June. Just warning everyone.
The best things to do at HHI are to beach, swim, and eat.
some folks like to golf and shop, but we like to eat.
they have great local rest. lots of them. You could eat all three meals for an entire week at a different local rest. and not even smell a chain rest.
There really is a lot to do with out it being a place like Myrtle Beach or Orlando. You can ride bikes, horses, boats. Take tours, sightsee, etc.
You will get a couple of gudie books at check in that will tell all that is to offer in way of food and activities.
I really think HHI is not a place to plan like we do at WDW. I feel it is more of a play it by ear kind of place.
You may get there and find you do not want to do anything but rest, swim, and eat. That is the ambiance that the resort has, a lazy summer river or lake retreat. (but at the beach)
p.s. One thing you would have to plan a long time in advance would be a Private Affair with Chef Gordon. I have not been able to experience this in 6 year of going twice a year because I always wait until it is to late. (he is always booked)