Hmm, maybe two weeks, then.

Some randon questions/thoughts:

Will it be just the two of you? (didn't know if any children involved in which case trains become a bit harder). If just the two of you are you hardy enough to take a night train or two? If so, you might cover more ground (albeit with higher degree of difficulty!) while saving a few hotel bills.

I think 1 week would be a stretch, at least to Austria. Do you know where you want to go in Germany? Two weeks definitely more doable if you can swing it.

Raileurope has some mixed train/car rental packages that you might be able to use. If you anticipate car only, take a look at Hertz and other web sites. You can get a quote for how much rentals are based on expected pickup/dropoff locations. It seems like there is little penalty for dropping off in a different city *within* countries, but that can change if you drop in a different country. All that data might help determine where you fly in and out of -- you might get lucky and find a cheap open-jaws flight, like arrive into London and depart from Frankfurt; less backtracking.

Either of you prone to carsickness when in the passenger seat? If so, stay off the squiggly roads if you cross into Switzerland!