18/4 is a good hedge. I'm not familiar with a broad range of shades, but some want shields on certain wires. How "finished" will the area be before the shades are installed? Is the wire to be left dangling or buried nearby? How much damage will be done if the wire is extracted and shades installed?

In one installation (I was not the shade guy) the shades were attached directly to concrete beams mounting the windows (beams to the sides of the windows too) and there were not many options for re-routing wires.