I have some artwork with various shadows. Some of the artwork needs to be adapted large format. I need to scale the effects in indesign with the object, but the shadow stays the same size. I have checked my indesign prefs and made sure the General options are;
[tick] Prevent Selection of Locked Objects
[selected] Adjust Scaling Percentage
I never scale effects, myself.
But I used to work in a large format output service. There's no reason you have to prepare the file at full size. They can scale the output from your original, if that makes life simpler.
Here's my take on shadows. The size of the shadow is related to the distance of the object off the surface on which the shadow is projected and is independent of the size of the object (once upon a time I was a physics major). making the shadow larger or smaller tells the viewer that the object is further away or closer to the surface. In my opinion, the best way to deal withthis is to define the shadows as part of the object style, and edit the style if you want to change the size of the shadow.