Where a couple marries does not affect the suitability of a wedding shower. And when you give the shower is negotiable too. Having the shower before or after the wedding is of no consequence. One of the reasons we give showers for weddings and new babies is to honor the institution and wish them well. That is a celebration welcomed anytime.
As far as hosting the shower, anyone who knows the couple well and cares for them can host. Whether it is a family member or a friend, as long as it is given with love and care it should be successfully received. Men as well women can host showers too! Times have changed.