We will be going to Kaiserslautern (for wife's high school reunion) then thinking of touring area around Heidelberg and the Neckar Valley. Maybe take in some of the Black Forest. Really interested in driving itineraries over 3-4 days.
Also, is it difficult to drive around Germany? Will we be able to find a rental car with automatic transmission? Also, what will traffic be like going from Heidelberg back to Frankfurt on a weekday morning to catch our flight?