Congratulations on your expected addition!
We also took a 1.5 year-old to Seaworld and the Magic Kingdom, and loved it! He's 6 now, and still one of my favorite pictures of him was the moment he saw Shamu come out of the water. - The look of wonder is priceless!
As the other poster said, there are quite a few rides at Disney you can take a toddler on with you, and where you have a big group, you will have no problem splitting up to go on wilder stuff.
Shows can be good for a little break. Unless she's scared of the dark at that point, it can be just what they need when the crowds get to be a little overwhelming from stroller-view.
Reserve your decision on character pics until just before you go. - Some kids will love them at that age, and some will hate them.
Take time at the little play areas. It feels silly sometimes, as you paid a big admission, and can find free playgrounds at home, but it recharges them when they get ansy sitting in the stroller.
Take a couple of her favorite snacks.
There is a baby-care center at all the Disney parks. They can help if you forgot anything, or just provide a break.
Can't think of anything else right now, but I'm sure lots more people will post as well. Have a great trip!