I'm from NC and my sister still lives in Charlotte. The traffic will kill ya', but there are a few good places to visit with a lady -

Carowinds - a huge amusement and water park and even though you're going to Six Flags in GA, this is definitely worth a visit

Discovery place - a HUGE science museum with a planetarium, acquariums an indoor rain forest. Way cool place for your inner geek

Verizon Wireless Amphitheater - lots of outdoor summer concerts. Maybe you could find a schedule online and see if anyone you two like is playing

Lake Norman, Lake Wylie and Mountain Island Lake - maybe rent a small boat or do some fishing from the banks?

My siter's husband used to ride mountain bikes with a group called the Tarheel Trailblazers. They had developed tons of bike trails in the area. I think they have a website too. Maybe bring or rent some mountain bikes?

I always take the wife to Carowinds and Discovery Place, she loves 'em. Hope this helps and that you have a safe trip!