Hi, Beth!
Congratulations on planning your first trip to Walt Disney World! Since you've asked a three-part question, here are my recommendations in each category (resort choice, activities and dining) for your family:
Resorts: My first choice for your family (and for your son, in particular!) would be a
Pirate Room at Disney's Caribbean Beach Resort. The Fuentes del Morro Pool complex is amazing, themed to a colonial Spanish fortress complete with 2 water slides, water cannons and a pirate shipwreck play area. Caribbean Beach is a moderate category resort. Two other great resort choices are Disney's Beach Club Resort (deluxe category) and Disney's Art of Animation Resort (value resort).
Activities: There is so much to see and do in the 4 theme parks that I don't typically recommend a lot of "extra" activities for families visiting for the first time. If your stay is at least 6 days in length, one tour your son may really enjoy is the
Pirate Adventure Cruise. Also, I wouldn't recommend park hopping to more than two parks in the same day.
Dining: Be sure to make Advance Dining Reservations for all table-service restaurants up to 180 days before your arrival. There are lots of great dining options, including the chance to meet Disney Characters during your meal. I highly recommend Chef Mickey's, The Crystal Palace, Tusker House, Hollywood & Vine, Be Our Guest and T-REX.
My response space is limited, so please feel free to send me follow-up questions for more details on any of the recommendations I've made!