If the volunteer is an elderly person I had planned that I would teach both volunteers and families. The family plays an important role in stimulating and helping to control symptoms.
If the volunteers are elderly people, I have planned to teach them and their families. The family plays an important role in stimulating and controlling symptoms.
If the volunteers are elderly, I have planned to teach volunteers and families, among which families play an important role in stimulating, warning and helping to control symptoms.