Congrats Rai.. we're headed to London too this summer.. I agree a bus tour is touristy but it's helpful getting a preview of the area and most of the guides are funny too!.. It helped when we went to Edingburg, Scotland.
Taking wife to theater in London.. and probably plan a day trip by train out to Bath or Cotswolds..
rest of the time at Museums/parks/out to eat and just walking around...
I'd give you advice on Germany.. but we were there way south of Berlin in Munich..