If you decide to visit Freiburg (nice little city), the "Busses Camping" on the edge of the city is excellent, very friendly and immaculate facilities even by German standards. We stayed there for two nights a couple of weeks ago. If you have a German emissions sticker (Umweltplakette) on your van you can then drive in and park close to the old town to visit it, or as we did, leave your van at the campsite and get the tram into the city for the day (the campsite is technically in the Green Zone also, but I was told the authorities won't bother you there, but certainly will if you park close/in the Altstadt if you don't have the sticker).
We also visited the Black Forest Outdoor Museum at Gutach (careful, there are two Gutachs, about 30 km apart!). We found it really excellent, and fortunately arrived early when it opened at 9am and had a lovely wander around, but the car park was completely full by the time we left at about 11.
If you have a couple of weeks you might I guess venture over to Lake Constance (Bodensee). If so, a visit to the Zeppelin Museum in Friedrichshafen is a must. We both found it a superb museum, even Mrs VD who isn't really an aviation fan.