Out of the following suggestions which would make for a better vacation for a husband and wife in their 30's?

The only one on your list with any kind of on island sightseeing is St. Lucia, its green and mountainous with the famous Pitons, sugar and banana plantations. The shopping is good there as well has great beaches but they are darker sand because the island is volcanic. If you want the sugar white fluffy sandy beaches go to Turks and Caicos, Cayman Islands, St. Martin, or Aruba. Aruba and St. Martin has the best shopping on your list. Also a great shopping place is Barbados with very pretty beaches and there's interesting caves to visit there. Punta Cuna is nice for relaxing but nothing much outside the resort areas, most people go and never leave their resort, like Jamaica. Anguilla is very nice, probably some of the best beaches in the Caribbean and outstanding restaurants. Antigua is another great place, good shopping and great beaches as well. Good luck with it.