One of the lovely city that we visited was Munich. The journey was abt 2 hrs from Stuttgart. Weather was lovely, kids weren't that bad either. All of them had their share of running & playing & lepas bebas so they weren't so cranky (we've had worst situation b4, right Fasha ;-) ).
Want to know more abt Munich.. ya go googled :-D .. but one thing for sure its worth the trip the city is beautiful with buildings age more than 300 yrs ago.