What a lovely houseboat, in a perfect location! It was exactly as described, and very comfortable.
We needed a car, so we followed the instructions and drove to the Park & Ride at Olympic Stadium (which is a short drive from Schiphol). The entrance to the Park & Ride wasn't obvious: it's the rightmost of the three barriers into the stadium's car park. Once inside, it wasn't obvious where to walk out (the exit for the tram is immediately to your right as you come off the ramp, and here you can also buy your discounted—not free—tram ticket). We took tram 24 to Vijzelgracht, which is a 2 minute walk from the boat. The boat is actually outside 985 Prinsengracht, not 965.
On return to Olympic Stadium, with a tram ticket that was used within the city centre less than an hour before, the parking is very cheap—we paid only €1 for an overnight stay. The following night we tried to park in the city centre (street parking on Prinsengracht is free after midnight, but we couldn't find a space). We ended up using an underground car park on the corner with Vijzelgracht (very close to the boat), but it cost €22 for a 6-hour overnight stay!
Overall, we cannot fault Olaf or Mark for their lovely home-from-home or their excellent hospitality. We highly recommend this AirBnB, and very much hope to return again soon!