We will be travelling from Cologne to Frankfurt with our 2 adult children during July. We want to spend two nights along the way and visit some castles,do a cable car trip and a cruise on the Rhine river. Please give me some advice on where to stay,hotels,where to do the boat trip,and what train to use. We don't want to stay in places that is too touristy but want to enjoy the beauty and culture of the area. I need some advice please! Is it better (cheaper) to travel from Frankfurt to Zurich by train or to fly?