Family history isn't just for active members of the Church. It can be a tool we can use to help find people for the missionaries to teach and to reactivate or strengthen struggling members.
Preach My Gospel, 2nd Edition has a number of sections on the use of family history in missionary work. Ward leadership may want to read through all the sections to gain ideas, but one section that is particularly useful is in Chapter 9: Find People to Teach under "Use Family History." Here is what was said.
Use Family History
Family history is another way you can find people to teach. Throughout the world, the Spirit is influencing millions of people to identify their deceased ancestors. Many want a stronger connection with their extended family. This can lead to a desire to find a connection and identity as part of God’s family.
What we sometimes refer to as the spirit of Elijah is the influence of the Holy Ghost drawing people to identify, document, and cherish their family members—both past and present (see Malachi 4:5–6).
In your finding, you might introduce people to FamilySearch.org or invite them to download the FamilySearch Tree app or the FamilySearch Memories app. You could also give them a copy of the booklet My Family: Stories That Bring Us Together. These resources help people discover relatives and ancestors and gather their stories.
Determine what family history resources are available in your area and how they could help the people you contact. The ward temple and family history leader can help people identify their deceased ancestors.
Invite people to share memories of their loved ones with you. As they do, they may feel the Holy Ghost testify to them about the importance of families in God’s plan. These moments can lead to natural conversations about the purpose of life, God’s plan of happiness, and the role of the Savior in that plan.
When appropriate, teach people the doctrine about why Church members do family history work and how it relates to temples.
Pray to be aware of opportunities to use family history in your finding efforts. Be creative, and become familiar with available resources.