Hi Joyce! We'll be on the same cruise!
We plan to walk around Copenhagen. I've looked at self-guided walking tours online. There's lots to see. We also plan to take a boat ride that leaves from the Nyhavn canal. It's reasonably priced and is one hour long.
For a nightlight, I bring battery tea lights. The battery lasts longer than the trip if I turn it off during the day. No plug needed!
I am puzzled what to do about water, also. We usually order a couple of cases of water that are delivered to our cabin on another cruise line. The "no plastic bottles" rule makes it tricky to figure out what to drink!