If you do end up in Savannah I suggest you join the Coastal Heritage Society
. They have a lot of family oriented activities including the Railroad Roundhouse Museum. One of my favorite times from when my kids were young was the camping trip at Fort Jackson. Usually done in February, you get to live the life of a Civil War soldier and sleep inside the casements of the old fort. This is a member-only activity but well worth the cost of a year's membership.