Welcome back, Robert! Both Tortola and St. Thomas are incredibly gorgeous islands to visit with Disney Cruise Line. So much is offered in each port, including zipline Port Adventures!
While I haven't yet experienced these two zipline tours, I have done quite a bit of ziplining, including on other Disney Cruise Line Port Adventures, and can tell you that it is an experience to remember! Even my teen daughter, who absolutely will not ride rollercoasters, adores ziplining! It's so different than a rollercoaster, so I do not think your son will have a problem at all. I will tell you that the first time we ziplined, my daughter was as nervous as can be waiting for that first zip across, but once she experienced that, she realized how amazing it is, and enjoyed every moment of the remaining lines on that tour!
The
Canopy Tour Zipline and Scenic Drive in Tortola and the
St. Thomas Tree Limin' Extreme Zipline Adventure both look to be fabulous. The views are truly amazing, as you'll be looking out over not only treetops but the ocean in the distance! The St. Thomas adventure includes something really unique, a yo-yo zipline that allows you to go forward and backward. If this is your first ziplining tour, perhaps that might seem a bit much for the first try, so maybe the Tortola adventure is best for your son. But, honestly, I bet he will fall in love with whichever you choose!
My suggestion would be to browse the other
Port Adventures in Tortola and St. Thomas and if there is a second you absolutely must do, choose the ziplines in the alternate port of call.
Have so much fun, Robert!
Marcy