We have about 3 days to travel from Munich to Ghent. We will have a car, if need one. If we can do trains, that works too.
I was thinking of going to Baden-Baden and staying 2 full days there and then head to Heidelberg, drop off the car and catch a train to Ghent.
Is that a reasonable trip or is there a better way to spend those days?
We do like visiting wine regions and haven't done that in Germany. Is that something we should do instead?

Well you could consider the Mosel Valley -one of Europe's primo wine venues with wineries all along the gorgeous river valley - one of most beautiful in Europe - stay in say picture-postcard Cochem or other wine towns and also hit Trier - one of oldest cities in Europe and has some of the most intact Roman relics anywhere - return car in Germany at say Trier and take train via Luxembourg City to Brussels and onto Gent.

Anyway book Germany-Gent trains at www.bahn.de/en - German Rail's web site and book early yourself online to get discounted tickets. Check www.seat61.com for lots on doing that - general info trains - BETS-European Rail Experts and www.ricksteves.com.