I have been to Martinique several times. It is a very beautiful Island. You will dock at Fort De France, which is the major town. The main shopping area is close enough to walk to and from. As you exit the dock area, bear left around the old fort . There is a square, or park area where arts, crafts, etc. are sold. I can't remember exactly how far it is but it's easily walkable.
I don't know if you plan to take a tour or not but Saint Pierre is a few miles away and is worth the trip. It was totally destroyed in 1902 along with all inhabitants by a volcanic eruption.
There was one survivor, a man named Cyparis who was in an underground jail for being drunk. There are shops, etc there now along with a museum. It's interesting to say the least.
You can get a lot of info. on Martinique at www. Martinique.org.
( I have read where some people claimed they didn't like martinique, that the locals were rude, etc. I have not found that to be the case. A smile, a thank you, please, etc goes a long way wherever we are ) Have a great time.