Which is better for a long weekend with the kids?

Savannah or Charleston (or somewhere else)? I’m looking to plan a weekend trip as a surprise for my wife. We’ll be coming from Charlotte, NC. We went to Myrtle Beach in July and I’m looking for something different this time. Here are the criteria:

[ul]
I’d like to keep it to no more than about 4 hours driving each way[/ul]
[ul]Activities friendly for young kids (7, 3.5)[/ul]
[ul]Near the water, rather than mountains (wife’s preference)[/ul]
[ul]Activities open in winter (January)[/ul]
I’ve been to both Savannah and Charleston, but without the kids and I wasn’t really paying attention to kid-friendly attractions. Other options would be Wimington; Hilton Head; etc.

Charleston has the Aquarium, the USS Yorktown, lots of parks, historic forts–but it depends on what your kids are interested in or how short their attention span is. If you get a good guidebook to both cities, there will be a section on kid friendly attractions.