Unless you are very unpractical and unadventurous, or not so healthy, or a little bit lazy, or just too rich, there's no need to book these kind of tours. Why?
Bicycle Rental: Available in all cities and bigger villages. Renting is cheaper if you do it in a smaller city and not in Amsterdam!
Tracks: It's not even necessary to buy lots of maps. The Netherlands are crisscrossed with signposted tracks, connecting all places.
Accomodation: Go for the 4500 families of 'Vrienden op de Fiets' (= Friends on the Bike). They allow other cycletouring members of the organization to stay in their home for a modest price. http://www.vriendenopdefiets.nl
Freedom: If you like a place, you can stay one more night for visiting some of their tourist attractions. A main disadvantage with Bike Barging is that you always arrive in late afternoon/early evening and that you leave (very early) the next morning.
Local people, local food: On the boat, the same cook prepares all the dishes and you're always surrounded by other tourists. If really interested in a country, going to local restaurants and staying with locals is far more recommendable.
Belgium: Everything I mentioned above, is also valid for Flanders (Belgium).