Unfortunately, Sandals does not offer tuxedo rentals on resort; however some resorts have contact information for local formalwear providers (varies by island). Keep in mind, due to the Caribbean climates, you may want to consider a light weight alternative for the groom.
A non-denominational minister customarily presides over wedding ceremonies, but if you wish to inquire about having a non-religious ceremony (justice of the peace) or a religious ceremony at an additional cost, please talk to your wedding planner.