I just happen to be in almost the same area at the time of this Do (have a conference in Aachen from 14-17 June), so I might be able to go to this.
I've been to PRG before. We did one of those free walking tours that are mostly designed to get you into the city and to find your bearings. Also went to Prague Castle, but only into the parts where we could get in for free.
Put me down as Interested, please.