If you family members have not done trek before then take them to a hill station like ooty,Mathairan, Mahabalashwa, and check there reaction and response as it might give you knowledge of how much capacity your family members have. plan a location after taking considering physically mentally and socially condition of each members of family. ***Most Important :find the family member who is afraid of heights, one who always created mischief, one unaware of direction, always lost in thought, slow one, lazy one, you need to keep an extra eye on these type of family members . As you don't want to regret after taking your family on trek.