Miami photography location

I'm not really familiar with the Miami geography, but we're ending our Transatlantic cruise in Miami and I would love to take a photo of the vessel after we disembark. The vessel is Celebrity Eclipse and she will dock at Terminal G, which is the terminal closest to downtown.

Will it be possible to park near the Children's Museum and get a shot of the vessel across the harbor?

There is lots of publicly accessible space near the Children's Museum. Just go next to the Watson Seaplane base and take all the pictures you like. How late will you be in Miami? Are you staying overnight? If so, head to South Pointe Park in the evening and watch all the ships leaving. It's spectacular there.

https://www.google.com/maps/@25.7828231,-80.1760476,3a,75y,231.3h,78.27t/data=!3m6!1e1!3m4!1stubya-CZyrDflEsJP_5GxA!2e0!7i13312!8i6656