We have visited St Maarten many times. Each is an expensive adventure, only because the shops there are so phenomenal. There are a variety of jewelers and electronic stores, as well as, clothing and the usual liquor and souvenir shops to suit any need. The best part are the prices. They are the cheapest we have found in the Caribbean.
The sightseeing on the Dutch and French side is abundant and will meet almost anyone's need for beach, sights and culture. As a bonus, you have the fact that this one island is shared by two cultures, French and Dutch.