I did the route as far as Mainz and then turned off to Frankfurt a few years ago. It's really lovely. Some thoughts in no particular order...
1. In Holland you can follow the green LF long distance routes, which are generally less direct and more scenic than the corresponding red signs. See http://routeplanner.fietsersbond.nl/ . The routes are generally very easy to follow, but I got lost coming out of Amsterdam because all of the signs point to suburbs rather than other towns.
2. The Rhine splits into many pieces in Holland, so there's no natural riverside route from Amsterdam to Arnhem. I would probably go the route Amsterdam - Hilversum - Amersfoort - Ede - Arnhem. There are lots of campsites north of Arnhem in the Veluwe national park.
3. The stretch between Arnhem and Dusseldorf has some stretches of heavy industry, don't try spending the night anywhere near Duisburg.
4. The 'mittelrhein' section between Koblenz and Mainz is absolutely superb, make sure to stay in a town in the valley somewhere between. Koblenz has a nice youth hostel which is a former fort, right on top of a steep hill though.
5. I've heard the section down to Heidelberg is very nice too.
6. Having more than one lunch is perfectly acceptable when cycling.
Hope this helps!