Since my DD is grown up and married now and talking of starting a family these are some great tips, to add to my Disney book for later on.
I have a few tips from when she was little.
1) Stick to their schedule, naps, meals, and snack times.
2) Character's at different ages could frighten them, don't push the picture op, its not worth it.
3) Make sure to have enough baby items with you for at least 36 to 48 hours, when flying, I mean everything, diapers/wipes, bottles/formula, several changes of clothing, food and snacks, small bottle brush, take a sponge slightly wet and add some dish detergent, let dry and cut up into pieces or strips, place in a baggie - to be able to wash out a bottle. You do not want to get stuck in a airport with out these items.
4) Garden Grocer and other delivery service are wonderful -
5) If you bring a umbrella stroller with you, these are great for airports, and such. But I would suggest renting a large stroller from one of the local company's. They deliver to and pick up from resort. They are really great for holding everything. cup holders, lots of under seat storage, canopy tops. My friends just did this with their 2 grandkids and said it was wonderful.
6) Swim diapers are a must.
7) Use the baby stations
8) Know that there might be a few hic-ups along the trip, but that your in the most magical place, and all is well.
As a suggestion it might be nice for you and your a 8 year old to have some one on one time. Maybe you could pick some rides together for just to 2 of you to ride together, maybe while the baby is back at the resort with your mom napping. Being the big sister or brother is hard work... Just a suggestion.