Hi Melissa,
Disney Junior shows are the best and your son has great taste! Tweak the bunny is my favorite...my kids are older, so I get to enjoy it with my cousin's young kids.
Unfortunately, The Octonauts are not currently at Disney World. They are super busy with their underwater sea adventures, and haven't been able to catch a break to head over to meet their fans. Since your son is a Disney Junior fan, I'd suggest you stop and enjoy
Disney Junior - LIVE on Stage at Disney's Hollywood Studios. It's a wiggly, dance in your seat (or on your feet) kind of show that is absolutely perfect for even the littlest Disney Junior fan. Your son can also meet
Disney Junior Pals in the Animation Courtyard. He gets to meet Doc McStuffins, Jake, and Princess Sophia, and you get to take fabulous photos of your son meeting his new friends.
I hope this information helps. Wishing you and your little guy a magical trip!