It is more subtle, but it looks like both of the other two children are crossing fingers as well. The boy in the middle seems to possibly be crossing his middle and ring fingers on his left hand and the girl is definitely crossing the same two fingers on her right hand. And Kate’s blurry hand on the kid’s waist makes little sense when nothing around it is motion blurred, unless, I guess, maybe she was yanking it away at the moment the photo was taken? But it seems like if that was the case the wrinkle/ fold in his shirt right in front of her hand would be moving too and not be as crisp as it is.