We had the same question prior to our cruise on Viking Sky from Antwerp in July. We also travelled independently. (Our dock was to be either Kattendijkdok or Willemsdok. We were told to try Katt... first and if the boat was not there, then Will...) I found a site on the internet with a map of Antwerp, so had something of an idea of the "lay of the land" and where our docks were. Just looked again on that map but could not see your dock.
I am sure you are aware that Antwerp has 2 train stations. The Centraal station is much closer to the docks than the Berchem station. It is not a long taxi ride at all from Centraal to the docks. I think your driver will be able to take you easily to your dock, though he may not know the boat. Our driver knew the docks well and gave us a mini tour through Antwerp on the way.
I suggest you contact Viking again, either directly or through your travel agent, for more specific information. (Sometimes it just takes a repeat call or two to find a representative who has the information you need.)