Recommend Freiburg and Titisee. Also a 'dip' in thermal baths like Bad Krozingen or Badenweiler (http://www.black-forest-travel.com/l...mal-baths.html) amongst others. You could always hop over the Rhine at Breisach to visit Colmar and the Alsacian wineries.

Do be aware of local bank holidays ...1, 8 14 and 25 May in France and 1, 14 and 25 in Germany.