Our TA said that we didn't have access to the RN until after the deposit, but I guess you could always call them anyhow and see who they send you too. I do have a contact now that I can call directly.
I believe you can cancel the cruise if it is before 75 days from cruising, so if you decide against it, you will get all your money back.
I hope that you are able to use the nursery. It looks really cute. I think you have 10 hours there for a 4 day cruise, and it is $6 per hour extra (it is not included).
I imagine the medical staff MUST have an O2 monitor, and I am hoping that because it is a disney ship they have more experience with putting IV's in kids since that is not as easy as adults.