In reply to JohnnyW:
Sounds like a great idea. My wife and I cycled by a circuitous route from Dieppe to Paris a few years ago, then used the bikes around Paris. We had a great time, doing castles and cathedrals.
We drove through Germany last summer. Can you go as far east as Munich? We stayed there for a couple of days and I thought it was a very interesting place, with echoes of the past and a very fresh, modern feel. In the English Gardens the city has what must be one of Europe's largest urban parks, and also the most landlocked surfing spot.
We went to Heidelburg, where we watched the World Cup final. It is drop-dead pretty, but is a tourist honey pot, a bit like Bruges. I am glad I have seen it, but I wouldn't go back there.
If you get down to Stuttgart, the paleantology museum is wonderful.
If you are driving through Belgium on your way, my tip is to see Ghent. I loved it. We went there on the way out to the Dolomites and then again on the way back. It is full of cyclists, is very attractive and has a great vibe. I'd certainly go again. We stayed in a hipster's house, found via AirBnB, and he lent us his bikes and gave us lots of good ideas for where to eat and what to see. We were there on the way back during the street theatre festival, when the place is absolutely buzzing and lots of fun.