I did much the same trip couple of weeks ago to Tannheim (just a bit further over).
The route reccomended to me which worked well was Abbeville Nancy (fuel and food stop[ total card required but usually someone in the aeroclub with one that will take cash in exchange] ..very friendly,offered FREE lunch). Haguenau then hop the high ground.
Haguenau/Strasbourge is where the bad weather is likely to be if there is any. From the clubhouse at Haguenau you can see the peaks of the high ground, so it is a good waiting point if the weather isn't playing ball.(as was the case with us!).
We were weathered in there for a day in torrential rain and then had to go north parallel to the hills and cross where they are lower.However ,landing there did give us options,rather than pushing into the really high ground in deteriorating conditions and daylight.
Whatever way you go I hope you have a good one!