Is using the term "family" strictly correct when we mean a group of the periodic table or is it just in general use (and should perhaps be discouraged in favour of using "group" exclusively)? At my highschool, other teachers refer to the transition metals as a family; is this a common practice?
Family is an informal term. Only a group and a period is an accepted terminology for the periodic table by the International Union of Pure and Applied Chemistry, a widely respected authority on chemical nomenclature and terminology.
The Wiki page of periodic table should be modified because a dubious and layman type reference (www.shmoop.com) for group (= also known as family) is being cited.