Welcome aboard, Amanda!
There are Port Adventures offered for every age in Alaska, so no matter his age, your son will have so many exciting offerings to enjoy with the whole family! I highly recommend any Disney Cruise Line Port Adventure that features an Exclusive Family Activity. Not only will the whole family be immersed in the culture of that particular port, and get an amazing tour, but there is a special activity for the family to enjoy that really lets the kids experience the history and culture of the people in that area. You'll see a few of these adventures with family activities in Alaska such as the
Annette Island Cultural Celebration in Ketchikan and the
Liarsville Gold Rush Trail Camp and Salmon Bake with Exclusive Disney Character Experience in Skagway. Check out the other exciting Port Adventures that allow kids his age to join in. Simply visit the Port Adventures page, click on the port, then choose ages 3-4 in the bar on the left. You've got so many amazing choices, Amanda!
My family enjoyed the Dream as our first Disney cruise as well, and were a bit worried about sailing on the Wonder since it was a smaller classic ship after our amazing cruise on the brand new Dream. Boy, did we find out we had nothing to worry about! Each ship is unique and offers magical experiences! The Wonder is actually one of our favorites, as we love the smaller, more intimate atmosphere and the fact that the classic ships have allowed us to really get to know the Cast Members better, creating a more magical trip each time! So, no worries about the size or age of the ship, Amanda! Disney does it right on every ship! Happy planning!