Individual therapy for each family member, not just the addict, is important for the mental health of both the addict's spouse or partner and children.
When seeking professional therapy, be sure to look for programs or counselors who are accredited or licensed (ask about what professional credentials, certifications and licensure they have). Does the therapist specialize in the issues you want to work on? Also, ask about therapy methods and approach -- not all practice the same flavor of therapy, and approaches vary from methods such as cognitive therapy to behavior modification to psychotherapy (also known as "talk" therapy).
Other things to consider are insurance coverage and expense, but ultimately the right therapist is the one with whom you feel most comfortable.