YES!!!!!
Some do, but cash is king on Harbour Island. There is a 1:1 ratio of USD to Bahamian currency and all places accept both so there is no need to change currency. Visa is the most widely accepted, Amex is accepted some places. If you show your US drivers license, some shops will drop the VAT for you.
Harbour Island runs on City Water and The Other Side has a well. Both are fine for bathing and brushing teeth, but it's saltier than we're used to so they don't recommend drinking it. Water is available in the main spaces of the hotel for drinking.
Sunscreen is something that is cheap here and expensive on the island unless the hotel provides it for you. Not sure if our venues do or don't, but will ask and update. Liquor- if you can manage to bring some champagne do that, champagne is very hard to get on the island so it has a huge markup. Other hard liquors can also add up and are more expensive. The island beer, Kalik, is super cheap and somewhere between Bud Light and Corona. Swimsuits, beach sandals, beach hat, multiple pairs of cheap sunglasses (in case you are like me and decide to do cartwheels in the ocean, drunk, with sunglasses on your face), shorts, a coverup, a few tops/dresses, one or two sweaters, sometimes the temps can get slightly chilly at night. And of course, your more formal wedding attire! Don't forget your -Deodorant -Chapstick -Anti humidity spray and strong hairspray for your hair if your hair is more than 1 inch long and you're not into your au natural humidity hair
Habour Island is sort of like New Orleans. You can walk with your booze, drive your golf cart while drinking booze, bring your own booze to the beach, etc. They are however currently very strict on Cannabis products so I would not pack any of that.
Golf cart or your feet
Yes! Valentines has an awesome discover scuba class with minimal book/pool time and a great ocean dive. They have other dives you can go on if you are PADI certified.
No. You will get bitten by a shark.
Conch and Coconut is probably your best bet, although many of the locals who hangout on the fisherman's dock will take you out as well.