It does indeed say you can get a 1A from a IS guarantee, but my PVP says that is incorrect, when I showed her just a couple of days ago. She sent me a booking sequence which cabins will be grabbed and it didnt include 1As. She said she will look into trying to get it fixed on the website.
So, you can get any 4A or higher category cabin, which will be 185 s.f. and Carnival gets to pick your location. This should be exciting, your first cruise, after your husband gets back. Enjoy and have fun