I thought I would hate Coco Cay but I loved it. Not everything costs extra. There are plenty of free lounge chairs on the beach under umbrellas. There are free food venues with good food. There are free beverages (water, iced tea, lemonade). There are pools and splash pads for the kids that don't cost anything.
Yes, there are plenty of opportunities to spend money if you want to. But you don't need to spend a dime to have a good time.