I'm sure you will just love St. Martin & St. Maarteen as you probably already know it is a duty free port with such things as jewelry, clothing, alcohol, perfume, etc at excellent prices. Also St. Bart is IMHO a very very expensive place to visit with outrages prices.
If my memory serves me correctly there is an excellent restaurant as you walk to-wards the town on your right. It has long flowing flowers going down the wall and you have to climb up the side stairs to get to it. It is just before you get to the city center (centre) and is painted white and pink. Great food and drinks there at a very reasonable price.
If you have time I would recommend you rent a car and tour around the island as it will only take an hour or two at the most. You will love this island I'm sure. Happy vacation