Welcome Aboard, Linda!
It sounds like you have a wonderful family vacation ahead, with three generations aboard a Disney Cruise! What fun you'll have, and you'll be amazed at all the activities that you can all participate in together, as a family! I've checked out the Port Adventures in San Juan, and found two that might be appealing to your all-ages sailing party.
If you're looking for some splashtacular fun, the
Isla Verde Beach Escape San Juan is a three hour experience that includes a lunch buffet of authentic Puerto Rican food. You can choose from a variety of water sports and rentals (at an additional cost), and you have access to the resort pool. Beach chairs and beach volleyball are included. This adventure is located at the Courtyard Isla Verde Beach Resort - a beautiful beachfront property with tranquil waters perfect for swimming.
If your family wants more of a "nature" based adventure, I recommend the El Yunque Rainforest Tour and Nature Walk. This low impact walk through the rainforest showcases some of the natural beauty of San Juan. The walk takes you to Cocoa Falls for an awesome photo op and a spectacular view. You can read all about this fun adventure
here. (Note: guests must be able to walk for up to one mile, and you might want to bring some ponchos - after all, it's the rainforest!)
There are lots of choices, but I think both of these would be fun for the whole family. I encourage you to use the filter tabs on the Port Adventure page to help decide which excursion is the best fit for your family.
I hope this helps! Please let us know if you have more questions as you plan. - Diane W.