Charleston is very pretty and a wonderful city to walk in. The battery and the mansions are beautiful. The Yorktown and other ships are interesting and fun, amazing how big an aircraft carrier is! The Citadel is nice to see also. Horse drawn carriage rides are nice and the city market is fun. There are some nice nearby sites- Boone Plantation, Drayton Hall, Cypris Swamp among some. I find Charleston more gentile than Savannah. Savannah can be a little honky-tonk which the teen-agers may like. Savannah has "midnight in garden of good and evil" and "Forrest Gump" things to see. Overall Savannah is a little more eclectic. Very nice visitor center in Savannah, Charlestons is so-so in my opinion. We went to Savannah last May and it has a mardi-gras feeling (open containers allowed, lots of drinking) which may or not be to your taste. My wife and I find Charleston more soothing and relaxing.
Hope I haven't confused you more- Jean and Bob