I am new to the forum (my 1st post) and wanted to offer my advice: I live in Charleston and formerly worked in sales with Hamburg-Sud.
Charleston should be added to your list: check google map and you'll see many viewing points to observe ship traffic. The SC Aquarium is a nice vantage point and your g/f could enjoy a tour while you spot. On the Mt Pleasant side of the harbor the Charleston Harbor Marina/Resort http://www.charlestonharborresort.com/
is in a unique position where vessels must navigate a tight turn and channel.
Both Charleston & Savannah have up-to-date websites.
Savannah is good for viewing and a rooftop bar/restaurant at the Bohemian Hotel offers a great vantage point. http://www.bohemianhotelsavannah.com/
Jacksonville is a bit out of the way for me, but I would advise to check out Mayport in the vicinity of the ferry. The harbor pilots are stationed there.
Hope all goes well!