Hi, Jeanette!
There are so many wonderful resort choices, it can be really hard to decide! With little Mouseketeers in your family, I would suggest
Port Orleans French Quarter in a standard room, requesting a room close to transportation. These rooms are just a quick walk to the bus stop, the food court, and even the pool is just a short walk away.
Your 8 year old will love the fun water slide, and you can enjoy splashing in the kiddie pool with your younger ones. If you have your stroller with you (and I suggest you bring a double stroller along) you can even stroll down to Riverside to check out their beautiful grounds, and maybe even enjoy some Catch and Release fishing at Ol' Man Island.
Caribbean Beach and Riverside are both lovely resorts, but very large and more difficult to get around. I think you will find French Quarter more convenient with your family's ages. With about 1,000 rooms, French Quarter is about half the size of the others.
A pack and play will be provided for you for your baby girl, and you can request bed rails if needed for your 2 year old (or request a second pack and play if that works better for you). Whatever resort you choose, give them a call a few days prior to your arrival to let them know exactly what you will need to ensure a happy time for everyone. Have a great vacation!