I started out by saying that she was a fool for even TRYING to take the oldest, regardless of the child's gender. As for separating the two the 16 y/o and 10 y/o most likely don't even realize they live in the same household already. Come on...
And so far the only thing you can say about your being the better parent is moral which is because you feel slighted that she cheated on you? I thought you guys sorta cheated on one another. But that has NOTHING to do with your parenting skills AT ALL... I am not the one who brought up morals - you did. And I am not judging either one of you. Heck, I am actually saying what was good for one, was good for the other?
ANY CHILD (regardless of their gender) will have a hard time being separated from their mother at the age of 10. That is not *old school* it is a fact. But YOU are the only one in your situation and YOU are the only one who can determine (or at least TRY) what is best for YOUR KIDS.
It is traumatic for any child to have to go through a custody battle and your *points* are full of a lot of suppositions and conjecture. The fact that the children told their mother one thing about who they wanted to live with, you another thing and the judge yet a third thing doesnt prove a thing, except that the children feel torn, as they would regardless of the circumstances.
Fact is, she put you in a difficult position by doing this all *last minute*. I supposed she was hoping that you couldn't/wouldn't fight based on your history. Well I suppose she figured wrong. Bottom line is custody is always modifiable. Ask Biteme. He will tell you all about it.