Look at Four Seasons on Nevis or Little Dix Bay on Virgin Gorda - both resort/islands have all of what you are seeking except you'll have to compromise a bit on the shopping as neither of these islands are known as shopping meccas, but they both have a few interesting shops you can visit. However, all is not lost. If you choose Virgin Gorda you can easily go to Tortola for a day to satisfy your shopping fix or if you go to Nevis you can take a short ferry ride to St. Kitts where you'll find all the shopping you'll need.

In my opinion, Grand Cayman has plenty of resorts that meet the requirements listed on your wish list and the island has lots of shopping but the island itself is not "low key" enough to meet your expectations.

Likewise, neither St. Kitts nor Martinique will have hotels/resorts that offer "great amenities, great suites and the incredible service" you included on your wish list so you'll probably be disappointed with those two islands. I'd cross those destinations off your short list.

Thanks for your help. I will cross them off the list.