While you are in St-Martin I would recommend Friar's Bay and Happy Bay for the Beach.
For the shopping I would recommend Philippsburg. Looks like they have a better choice and you cand get a better bargain than the French side. Besides bewafre of the Euro Change.
Sighteeings, I would recommend driving to pic paradis, the view is so pretty on the all island, it's a liitle bit of a hassle to make it up there but it's worth the drive.
Bar, the BIKINI BAR on Orient Bay is fun, while you are in Orient Bay you van walk all the way up to have a dring at the Papagayo, ( clothes optional...oooops ).
Dining, I recommend THE BOATHOUSE at Simpson Bay our favorite spot for seafood, great atmosphere, I would recommend as well LE SAINT-GERMAIN at the Marina, Marigot.
Don't miss THE SUNSET BEACH BAR, at Maho, good entertainment, watch those planes!!!