Given your son's interests, I'd recommend Epcot or Animal Kingdom. Epcot has World Showcase, with eleven different countries' pavilions to explore. They're rich in cultural goodies (some have films or exhibits to enjoy), and you could buy him a passport kit to have stamped at each one, which would be a fun souvenir to take home.
The Future World section of Epcot is less technologically oriented than it used to be, but there is still a lot to learn about the natural sciences, and specifically marine biology, in The Seas pavilion. He'd probably enjoy Turtle Talk with Crush there. There is also a new science show called SpectacuLab he should check out in Innoventions.
Soarin' Around the World and Spaceship Earth are wonderful Epcot attractions for kids of his age. Not too sure if he'd be that into Frozen Ever After, given his lack of Disney interest. Living with the Land is a must for folks with an interest in horticulture.
Another plus with Epcot is that you'd be going during the Flower & Garden Festival. There will be beautiful gardens, topiaries, and even a butterfly house to explore. It's just a gorgeous park at this time of year. Really enjoyable to walk around. There are tasty treats at the kitchen food booths, too.
Animal Kingdom would be right up his alley as far as his interest in wildlife goes. He'd love the animal trails and the Kiliminjaro Safaris. I'd strongly recommend he enroll in the Wilderness Explorers program, too, which assigns kids certain "tasks" to complete throughout the park, and is educational while being extremely fun. The new bird show might be open by then as well. The number of rides at Animal Kingdom that would be suitable for his age group is rather low, however.
Pandora is the new must-see land at Animal Kingdom. If you can get a Fastpass for Avatar Flight of Passage, it's an absolutely amazing attraction. Otherwise, unless you get there about an hour before Rope Drop (park opening), you probably won't be able to ride it. The lines are extremely long.
Once you nail down a specific park, make sure you select your Fastpass+ reservations at 30 days out, if you're staying offsite Disney property. I'd position them in the afternoon hours, since lines are longest then. If you want to make an ADR (Advanced Dining Reservation), take a look at some restaurant menus in advance. It might be difficult to find any openings now, but the parks also have great counter-service restaurants that don't require ADRs. Be sure to download the My Disney Experience app to access wait times while you're there, and to be able to modify your Fastpass+ reservations, or try for a fourth, rolling Fastpass after you use your first three.
I hope this wasn't too overwhelming! I'm sure you'll have a wonderful day, whatever you decide to do.
