Yeah, throwing in the child part is pretty funny. That shows desperation, in my opinion. I didn't think that would be brought up. I think they are hoping something, anything will stick.
Typically they try a case for the highest charge and then at the end throw in that they would like lesser charges to be considered by the jury. That keeps the defense from defending all of the lesser charges during the trial. But they are supposed to know that and be defening against it any way.
The defense acted like it was a trick from the prosecutors, which it wasn't because he knew they could do that, but it was a good act on his part and maybe the jury will think that the prosecution are trying to get one over.