We couldn't find much on Cruise Critic or Trip Advisor for things to do on St. Vincent and we were going to be there on Christmas Day so we chose to do an excursion through the cruise ship.
We chose to do a catamaran trip that involved snorkeling, lunch, and an hour to enjoy at Princess Margaret Beach on Bequia. Bequia was amazing. The water was crystal clear and there were many shells to snorkel and find. We learned later that there is a ferry that will take you to Bequia for the day, but I am not sure how much it costs. I would highly recommend getting over to Bequia as it's officially my new favorite island due to the long stretch of beach and crystal clear water.
We did have friends that chose to take a taxi tour of St. Vincent and were taken to a waterfall and some filming sites for Pirates of the Caribbean. They said it was a great day and their 10-year-old daughter really enjoyed it!
If you have questions about visiting St. Maarten or want to book your next vacation, you can visit www.thegypseatraveller.com and click on "Schedule Consult" to choose a date/time to zoom with Libbi, The Gypsea Traveller