We got back from WDW three weeks ago and I just hit six months at the time we left. We had a fantastic time and I have to say that the slower pace of everything was a big part of our success. My mother has bad knees so she doesn't walk quickly, it was our first trip with no strollers (DD4 and DS turned 7 on the trip), and I was definitely waddling a bit. So the majority of our group moved at a snail's pace and that was fine. We didn't plan too much, stuck to our favorites, adjusted when needed, tried to swim every day it was warm enough, and got to bed early. I put in 42 miles of walking that week, but it was fun and I didn't overdo it. My biggest piece of advice is make sure you have good shoes and accessible water (bottle, camelbak, refillable mug, etc.) and keep hydrated by drinking all day long. There are restrooms EVERYWHERE so just use them rather than avoid drinking. Two days into the trip my son stopped bugging me about needing a bathroom break after every attraction.
I had morning sickness with all three of my pregnancies and this last one was the worst, but it cleared up by the beginning of month 5. I have to say I always feel better outside walking around though. In fact with my first pregnancy, DH and I went to Disney for a belated honeymoon and my morning sickness ended on Day 2 of our trip. That was a very pleasant bit of Disney pixie dust.
My son has yet to take his first trip, but he likes to talk about when he went to Disney in mommy's tummy, as if he could remember!
