Years ago the wife and I took a horse and carriage tour of the city. Recommend highly if they still do the tours.
They still do these, and I think it’s a great way to see some of the city and get history at same time.
Downtown- waterfront park, battery, rainbow row, and the market; They can all be walked within a reasonable time but could wear out a child. They aren’t just for history either as the park and battery have great views. I went to Fort Sumter years ago, and it’s almost a must if you are into the Civil War. Since we stay on IOP, we only have lunch when we go at one of the several restaurants near the market. There is also an aquarium, but I haven’t been (my kids may have).
If you are staying near Sullivan’s Island or IOP, Fort Moultrie is a smaller, lesser known location right on beach on Sullivan’s Island. It was an important location to occupy if troops were trying to take Fort Sumter. Also where Osceola is buried. Sullivan’s Island has a great strip of restaurants but gets busy early.
Patriot’s Point is cool and many things to do, but we haven’t been in years as well as other plantation tours.