Originally Posted by SquirrellyMama:
I would think that you could talk to dad yourself. Did he sign the contract? I imagine he has rights also and can choose whomever he wants.
I personally don't think it is very classy of him to use her if she is his cheating partner. Not that it was classy to cheat in the first place.
Good luck 
K
So true!
I would suggest for the kids sake, to use an alternative person to the make the transition easy on everyone, included you & the other children in your charge.