I am originally from the Charleston area and have lived in Savannah as well. The issue with either city is that you have to drive a good bit off of the interstate to see anything of interest or get remotely close to the coast. Both cities are amazing if you want to take the extra time to see them. However, I am not sure if that is the sort of experience you are looking for given the fact that you are commuting to Disney during that time.
Two hours north of Savannah on 95 wouldn't have much to see except really small towns. Beaufort, SC is also about halfway between the two and is a really beautiful town. Once again, it will require you to get off 95 a good ways though.
Honestly, I've always hoped that people outside of the state don't judge South Carolina by the places most people see...I-95 and Myrtle Beach.