If they will be cruising and want to be close, Anthony's Pier 4 on the water is pretty nice and close to the docks.

Lez Zygamates is a short walk from south station, reasoanble price, good wine selection and good french cuisine. I usually go there for lunch, never done dinner, but I've always enjoyed it. Will probably run them closer to $150 or so.

Keep in mind some of those harbor cruises are dinner cruises. Make sure you book a non dinner one of course.