As many others have said, lots of toddlers the world over have used regular potties without a problem - yes, you may have to hold her or lift her up, but it's really not a big deal at all - certainly a lot less hassle than dragging a baby potty all over the place.
Another option is the child care centers. They have tiny kid-sized potties. They aren't always convenient, though, ot where you happen to be.
If you aren't comfortable with the cleanliness of the bathrooms and felt the need to use the disposable mats on the last cruise, I'm going to guess that you won't be comfortable with the high chairs at WDW either, so you should plan on bringing whatever you need for your daughter to sit at a table.
Another option is the child care centers. They have tiny kid-sized potties. They aren't always convenient, though, ot where you happen to be.
If you aren't comfortable with the cleanliness of the bathrooms and felt the need to use the disposable mats on the last cruise, I'm going to guess that you won't be comfortable with the high chairs at WDW either, so you should plan on bringing whatever you need for your daughter to sit at a table.