I don't really take advantage of the discount coupons but I'm sure you could probably get some of those discounts directly from the restaurant's websites. I know that the Paris Bistro had coupons on their website and lots of others as well. The only convenience I could see is that the Caribbean Card puts all of them into one neat package but at the same time, isn't there a charge for it anyway?
If you get it "free" with the purchase of something else, and when I say "free" you are not paying more to use their services and get this card for "free" (or else it would not really be free), then sure, you could take advantage of those coupons to save some money if those are the restaurants and activities of interest.
Most discounts (not all) are for a free drink or appetif, and usually at those restaurants they usually offer a free appertif anyway. To me, that really isn't a special savings if everyone else is offered the same as well.
My best suggestion is to scan the web for the restaurants you are interested in and go to their websites. See if there are any coupons and then print them out before you leave for your trip. They will probably be the same discounts you'd get with the Caribbean Card.
Life is not a child's game of follow the Leader. Instead, life is more about finding one's own purpose in life....your life's plan, and then making a positive difference on earth.