Congratulations! You're beginning a big adventure.
I have to say that I'm amazed and awestruck by those parents who took their babies at 1 week, 1 month, or even 6 months. At 1 month postpartum, I was a zombie not fit for public appearance-- let alone organized enough to coordinate travel arrangements and haul all the baby support system stuff along on a big trip! Wow. When my kids were newborns, I thought it was a major accomplishment to get out of the house and go to McDonalds.
Anyway, I read somewhere, and I liked the sentiment-- that if you are taking your child as an infant, you're not doing it for your baby's sake. You're doing it for your own. Which is just fine, but I guess I wouldn't kid myself that I was doing it for my baby's benefit. I would say DL is not the ideal vacation for a baby; babies like routines, and you're likely to be knocking them out of their comforting daily routine. It's not like it's really bad for them or anything, but really, it's for your own delight of the experience of introducing your baby to your favorite place. Babies like to see lots of colors, listen to music, etc. So they'll probably enjoy it, at least until overstimulation sets in. Then they will likely get fussy and cranky, and you might get frustrated at how limited you are by your darling little dictator.
Wait a minute, I just realized. I think DH is that same way. Gets overstimulated, fussy and cranky. Who's the baby here?
I think toddlers, at one year-18 months, can understand so much more than they can articulate, and they can really enjoy the experience! They won't remember it when they get much older, but it will add to their experiences and give them lots of new sensory input.
3-4 is when they'll really start remembering it. What a fun age. Our kids were 5, 10 and 12, and they each had fun in their own way. DD5 was wide-eyed with wonder. DD10 was excited, enthusiastic, hyper, hopping all over and cracking jokes and generally having a ball. DD12 was acting like she was too cool (well, besides feeling under the weather which didn't help) but she loved the sense of freedom when we let her decide what to do, and to ride the big rides. I haven't seen her so excited for a long time, as when she rode Space Mountain 3x in a row! She was grinning and laughing like crazy! She is so excited for our upcoming trip!
You'll have a wonderful time with your son at any age. Enjoy the ride!
