The Thomson excursions in the Caribbean are on their web site as well as the duration and cost. Occasionally they offer additional excursions once you board (or indeed withdraw previously advertised ones). As this is the first time in years that Thomsons are in the Caribbean the list on their site should only be taken as a guide. As you arrive on the ship the full list will be available. Hope you have a great cruse. The Destiny is a lovely ship if you discount the vibrations.
Usually one gets the list of excursions about six weeks before departure. Sounds as if Thomson need to get their customer service in order if they can't be bothered to let you know this.
The excursions for each destination should be available on the Thomsons site, at least they used to be although when I tried earlier the site seems to be having problems.