This sounds like the best idea ever. I can't believe no one has ever come up with it before.##
The only way this happens is with a very details legally binding contract, where:
1) She pays you to impregnate her.
2) You are free from any future financially liability.
3) She is placed under a gag order in revealing details about you without consent.
Even then, the (lack of) rationalisation of bringing a child into the world under those circumstances is borderline negligent and insane.
If she loves kids, then she should become an au pair or look into adoption. If you think catching up after 20+ years is a good idea, maybe you should stick to something more simple like getting a dog.