You do realise that, when you arrive in Germany, everything will be closed and will remain pretty well closed throughout your trip. Also the weather will likely be horrible.
Oh yeah I'm aware. Frankfurt is just the first stop to visit friends, after that it's probably off to the Swiss Alps, etc.
The fixed dates are annoying, but unfortunately that was the only way to do this because of vacation time and so on.
Thanks for the advice guys, I appreciate it!