Mark is right. My wife and I have done many tours in Holland( she doesn't like hills)
We have tended to use B&B's or small hotels (she doesn't like camping

)covering 50 to 75 miles per day. I would recommend trying to get to the Veluwe for some time as the forested areas are beautiful, but you could also go up over the Islands.
Feel free to pm or e mail me and I'll point you in the right direction. We booked our last trip entirely on line, by the way.
John