I think you might be out of luck. The particles are linked to the 3D Null, which you could parent to another null and scaling that up should probably scale up the movement positions, but the particle effect itself will also need its particle scale and number of particles altering manually.
I suppose you could use expressions to multiply the current values by the same factor? That might work, something like:
Position: [value[0]*2,value[1]*2,value[2]*2]
Or particle number: value*2