hi
Shrinking the volume should be ok and not impact your LUN as long you leaving enough space for snapshot reserve ( vol show -fields percent-snapshot-space), if you exceed this, the LUN will go offline.
and of-course also putting here another warning (less directed for you - but more to whoever find this in google in a year time) never shrink the LUN itself without a dedicated tool that can adjust on OS file system layout (for example snap drive)
gidi