Update: I did it. Got on Carnival Elation in Mobile, and didn't leave until we arrived back in Mobile a week later.
Pools and water slide were open and nearly empty, and I was often the only one occupying a deck chair. The dining room was closed for lunch (as I had expected), yet this gave me the opportunity to go to the buffets, something I seldom do as I don't like crowds. (I likely would have missed the wonderful Mongolian Wok, otherwise.) I read one book and started another. Went to the gym and could keep my usual routine as there was no wait. Took a few naps in our cabin.
So, that's one more item crossed off the bucket list. I don't know if I'll do it again on a 7-nighter, especially if it goes to Cozumel. It's a favorite port, and I missed the great time my husband and son had there on this cruise. That was the only downside.