This is the route as sent out with the invitation. It is probably just about detailed enough to navigate by. We used a few sets of maps to navigate, and also some more random methods such as the well known 'I am absolutely certain we have to turn left here' and 'I could have sworn that that was the right road' (their Dutch equivalents of course!).
Map 1 Culemborg to Moerdijk is here.
Map 2 Moerdijk via Renesse to Rotterdam is here.