The NPC-02446 motor is advertised as "great" for lightweights.

The data from Robot Marketplace gives this motor a 500W rating.
You can get a heavy moving with those, but you won't be happy with the results.
If you want any acceleration, you'll have to use a gearratio of 6-7 to 1 with the 4" wheel. Trundling around @10kph. But you'll be there in a jiffi.