Average high temperature 90 F.
Average low temperature 80 F.
Average temperature 84 F.
Average water temperature 82 F.
Average wind speed 18 mph
Average rainfall 1 inche (20.3 inches annual)
Average windspeed 18 mph
You should NOT have a problem with weather in August. The water is warm and the weather is hot, cooled by thost average 18 mph tradewinds. Our one August visit we awoke our first morning to a rain shower which had just ended with a beautiful rainbow. Those were the only drops of rain we saw.
As far as luxurious all inclusive resorts...Occidental and Riu are the two most expensive, but I do not think you see as much talk about them as you would think in that because they are expensive BUT mediocre all inclusive, when compared to the 5 star all inclusives found in such places as Mexico. If you read the reviews of both resorts on tripadvisor.com you will see they are very very mixed. Imo, there is a reason for this: inconsistent.
The Westin offers an all inclusive option, but it has many restrictions and surcharges and imo, is not a "true" all inclusive. The Holiday Inn and Amsterdam Manor offer all inclusive options as well. Sister resorts, Divi and Tamarijn are all inclusive only, but not considered luxurious. Our favorite resort is still the Radisson, but there really is nothing which beats the "all" oceanfront rooms at the Tamarijn.
I vote for the Hyatt as well. Great staff, great rooms, great location. I'm going to stay there for a few days over the summer due to business obligations or else I'd stick to my house. It'll be nice to have room service and someone else's pool for a change.