If you want to get close to the planes IMHO the best is on the beach at the west end of the runway. Hold on to your stuff..
My personal list of mustdo's while on the island: Mark's Place is a long time favorite for a more casual dinner; beach at Baie Rouge; shopping for booze including Guavaberry liqueur in P'burg; and dinner overlooking the beach in Grand Case.
enjoy,
/pbz