Welcome back, Deanna! My family loved our most recent visit to Key West with Disney Cruise Line. There are plenty of attractions to visit and fun things to do on that island.
The conch train tour is a lot of fun, because the kids thought it was fun to ride the little train. However, depending on which dock the ship pulls up to, you might get a free ride anyway! When we docked there, our ship docked at the naval base, and since we couldn't walk around the base, the little trains took guests from the ship to the heart of town. That was a nice treat! However if the ship pulls up to one of the other docks there, you won't get that ride.
Any 8-year old boy is going to love the Shipwreck Treasure Museum in Key West, pretty fun for little pirates. There are a few different Port Adventures that take guests there, but since you're looking for beachy ideas, if you book one of the water adventures I'll suggest, you'll still have plenty of time to explore Key West on your own after your adventure, and you can walk over to the Pirate Museum on your own!
Disney offers two adventures in Key West that are low-key and relaxing but still exciting an offer beautiful views. Both the Catamaran Sail and Snorkel Tour and the Glass Bottom Boat adventure offer guests the opportunity to head out into the water to view the beautiful sea creatures on the gorgeous coral reef, either from onboard with the glass bottom boat, or in the water itself on the snorkel tour.
Disney doesn't currently offer an specific beach days at Key West, but when you arrive in Castaway Cay, Disney's private island, you'll have the best beach day of your life, so I promise you won't miss out! Have fun!