Hej Loon,
You got 2 weeks- gonna visit family and see Berlin & Prag ? And kite ?
and go to Portugal ? wheew.
Do yourself a favor and dont try to do so much. Forget the cities- full of tourists. August is main holiday for most of Europe.
End of summer (end of august) kiting is poor in N.europe- if the weather sucks, rainy and stormy- then there is wind- but often gusty, turbulent and frequently full of lightning.
My recommendation would be to go to rent a car and head towards NW coast of germany towards sylt and drive north along coast up to Klittmöller. - bring wave board if you have one, but there are good flat water spots too. Stop at some small towns on the way and soak up the rural/ small town scene. You may get lucky with wind.
Portugal is nice- you could go all in - Ive been to Esposende- if you do that, thats all you should do for a week+- rent a car- go into Porto for a visit if not windy and drive north to the spanish border to Viana do Castelo- good kiting there too. I went there for a week in august and had only one day of wind.
You want wind in august - go to Naxos or Paros in greece
BTW- i am american living in south sweden on Baltic since 1984 and been around europe a bit in those years.