Hi Katherine,
A first trip to Walt Disney World is very special!
Depending on his age, something as simple as buying him his first pair of mouse ears, his
first haircut at the Harmony Barbershop (with a special surprise!) or a 'Mickey Mouse in a Glass House' balloon will give him special memories for life.
If you are looking for a special activity (and again, depending on his age), check into the
'Pirates and Pals Fireworks Voyage'. This is a swashbuckling cruise with a humorous pirate guide. It begins at the Contemporary Hotel with pirate 'grub', then you will head off on a cruise of the sparkling Seven Seas Lagoon. The amazing evening ends with a viewing of fireworks over Cinderella's Castle! This is something the entire family will enjoy!
Katherine, I hope this helps. Have a wonderful family time together.