In this video, I do not see anything significant r/t body language other than neither poi appear aggressive. Slow that video down and I imagine we see two men casually strolling past the kids pausing shortly to speak to the kids. What I do notice is that poi 2 never looks back to see if the kids are following him. He either knows them and is confident they will follow, or he goes on his way oblivious to the fact they are following him.
LE teased us with a small section of this video. We do not know how soon the other child returned, or tbh, whether only one child returned to that area or if this was even the last known sighting of CC.
As for the father's body language in his live video, I just do not think it can accurately be assessed. Emotion, fatigue, and life experiences all play into how one reacts to stressful situations. This would be stressful to him regardless of whether he is involved or not. I read very little into his words or body language in his lives.
Birmingham has a large homeless population, many of them transient. This could be something to look at, too.