If you only do one thing as a group while you are here, make it this. The Scenic Railway leaves from the restored 1905 depot in downtown Blue Ridge and follows the Toccoa River for thirteen miles, running slowly enough that you can watch the water the whole way. The round trip takes about four hours, with a two-hour layover in the twin towns of McCaysville and Copperhill, where you can eat lunch, browse the shops, and stand with one foot in Georgia and one in Tennessee on the state line painted down the sidewalk.
It works because it suits everyone. Grandparents get a comfortable seat and a view. Kids get open-air cars, a real locomotive, and permission to hang out of the window. Nobody has to drive, and nobody has to agree on anything.
Book ahead, especially for autumn weekends and the Christmas services, which sell out weeks in advance. October is the obvious highlight for leaf colour, but a summer morning run is quieter and cooler. The ticket office is open 9am to 4pm daily. Bring a light jacket for the open cars even in warm weather, and pack a few snacks for the ride out.