[Dottore]

A couple of comments:

1. The museum at the Hockenheimring is IMO not worth a stop unless you are there and have the time. I wouldn't go out of my way for it. It's very small, and mainly has old motorcycles.

2. The Schlumpf on the other hand has one of the most outrageous collections anywhere, and is well worth the trip. Flying internationally to get there your best bet would be a connecting flight to Basel CH. From there it's less than an hour by car. Be sure to leave some time for the museum shop as they sell lots of cool stuff for gear-heads. Not much to do in Mulhouse otherwise IMO...but once you are there you are of course only a few hours from Burgundy, and the finest wine country in Europe. (The region between Beaune and Dijon is one of my favourite areas of Europe.)