In my adventure to Grande Cayman in 2002 August 23-August 31st I did not have any issues with storms. I know we can not predict the weather but the last 3 years at the same time my friends have gone again and again and they did not have any weather trouble. To answer your question about Grand Cayman having enough, well it all depends. If she likes to sunbathe and just relax, with the occasional shop at places and check out a few sites then you will be fine, but if she expects more than that, then it might be a tad unsatisfying.
There are plenty of things to do, like Stingray city, you can do that with Non-Diver and there is The turtle Farm, along with the many shop in Georgetown, I will say though, once you have seen a few of them they all start to look the same. There are some wonderful restuarants there and you can wine and dine her in that department, a favorite place of mine is the grandoldhouse (
www.grandoldhouse.com) this is a beautiful spot on the island and the food is spectacular. I dove either a 2 or 3 boat tank dive everyday, so therefore the rest of the afternoon would be just hanging out by the pool resting until dinner time. If your girlfriend isn't excited about diving I promise you she may change her mind, that's if she is a diver already. If I could become a mermaid the place to live would be Grande Cayman. The diving is so easy and relaxing, and the colors you will see are fabulous, it's like someone melted a million boxes of crayons down there. I never wanted to come up!
Yissak
"Live it while you can"