Is it permissible to shorten the prayer when visiting family and in-laws 300 kilometers away from the workplace?

It is obligatory to complete the prayer upon reaching one's hometown, as the concessions of travel cease. However, it is not obligatory to complete it in the wife's hometown, and shortening the prayer is permissible, unless one intends to reside there for four days or more, or if the wife is a resident of that place and the husband traveled to it, in which case he must also complete the prayer.