Well, first I would recommend they didn't breed them, as there are enough cats out there needing homes as is. Not to mention the slight odballness of mating a leggly, long nosed, short haired cat to a long haired, short nosed cat. Why??
If they are still all for it, your mate has a lot of reading to do on mating, pregnancies, what can go wrong, how to monitor a preggie cat and then the kittens and be prepared to fork out a lot of money if things happened to go wrong (ie an afterhours caesarean). Plus the increased chance her cat might get sick if something went wrong. Do lots and lots of reading on the internet (as I don't think you'll find registered breeders will be particularly keen to help you with this haha)
Also to note, will be that your Dads Persian should be screened first for PKD (polycystic kidney disease) as its hereditary in persians in particular and any cats that are used for breeding should be screened first to make sure they do not have a problem. I believe it involves an ultrasound of the kidneys.