R.R.
As much as it may seem they're not doing enough, I believe they are putting their hearts and souls into the investigation, no one likes it when children just vanish. They have to think logically and strategically and with no evidence the girls are in the area they were last seen in they have to pursue that theory, so at this point civilians are best utilized in spreading the word of their disappearance. Talking to people who saw them earlier that day may turn up clues as to who else was in the area or that they interacted with, and who the police should, if anyone, focus on. The family members will likely be interrogated over and over, they are always the first suspected and have to be ruled out, I know this firsthand too well.
I personally could not do the job of investigators. When my son was kidnapped I saw many turnovers in the DA's office over the years, they simply could not handle the anguish over and over again, it affected their personal lives and their families. Kudos to the police and community for the job they are doing.
God bless Lyric's and Elizabeth's family and friends, and everyone involved in the effort to return them home, all are in my prayers, I know this is hard.