Hi Kimberly,
Welcome to the Moms Panel! Not only would your son benefit, YOU would benefit too! I have found that a Disney Cruise Line vacation is by far the easiest vacation you can take with toddlers. Of course there isn't really a lot that is "easy" when it comes to the day-to-day dealings with a little one - but why not give yourself the opportunity to let someone else take care of the cooking and cleaning for a few days. Where else can you have your beds made (and turned down) each day, fresh, healthy foods prepared and available 24/7, and as much or as little entertainment that you and your kids can tolerate?
We love cruising because there is enough to see and do onboard, yet it is wonderful having the quiet comfort of your stateroom only a few minutes away at all times. There are no busses to deal with or dining reservations to make. Once your son is three he will be eligible to participate in the
Oceaneer's Club which offers plenty of supervised activities for the little ones - so maybe you could pamper yourself at the spa for a short while, you've earned it!
In all honestly, I highly recommend cruising with little ones. They won't be able to read the activities schedules, so they can make very few demands. Often they are just happy to swim in the pool or dance at one of the many family friendly parties onboard.
One last thing worth mentioning is that you would save a little money by sailing before he turns three, because you would not have to pay cruise fare for him - simply the taxes and port fees.
Good luck with your decision!