I did a ride down the Rhein & Mosel once when I was stationed there in the AF, but it was 1983 and I was on a department store Huffy then.
Beautiful place to ride. One strong memory is riding along the Rhein, eating cherries out of my handlbar bag. The Germans treated me much differently on a bike than if I stepped off of a tour bus with 100 other Americans.
Haven't done anything in the other countries you are visiting though. Afraid I can't offer you any good advice that is of current use, but wanted to say to have fun! (As if you need my approval for that!)