Pat,
Since your son is in the military, perhaps a tour of Civil War sites might be appealing. Try here for a starting point. I have been to several of the Virginia battle sites and enjoyed walking on historic ground. The James River area is also worth a trip. Colonial Williamsburg and Jamestown plus the historic plantation homes along the James River make this a memorable day. I was there in the summer, not sure about doing this in the winter.
Another option is to head south and hit Myrtle Beach, Charlestown, Savannah and the islands off the Georgia coast: Sea Island, Jekyll Island, San Simons Island. Or head a bit further south and hit Florida. St. Augustine, Daytona Beach, The Kennedy Space Center. That is a warmer option than Virginia in Dec. Hope this helps with your planning.