We are leaving in less than a month for our first cruise (7 night Eastern Caribbean sailing on the Fantasy). For St. Thomas, I was only able to book 3 out of 4 of my family on the Secret Sands Beach Getaway excursion. I have been checking regularly to see if I can add the last person but I'm wondering what I should do if I don't luck into that last spot. A friend suggested that I go to the excursion desk when we get on the ship to see about adding another person. When looking at the excursion specifics, it says the bookings are considered final and non-refundable at 3 days before the cruise leaves such that keeping a reservation for 3 people with the hope of adding a fourth might be regrettable if it doesn't go my way on the ship. I'm reluctant to book something not through DCL in the event that something goes sideways. Any advice from seasoned cruisers on how to handle this?