I passed through this.
Filed application with old passport of my child. And after that i applied new passport for her.
Meanwhile, PPR came. Replied to that email with change in passport number and details.
Then, i sent the new passport only with copies of old one and with an explanation letter for stamping entry visa.
All processed without any issues.
But, when i received passport back with visa, they gave the entry time for all as per end date of first passport of my child. This means, i did not received 1 year time frame. I received visa in august and need to enter before this December because that the expiry date of my childs first passport. I can travel with her new passport.
So when you send details regarding passport update to PPR request email, mention this specifically
Other than that no issues and its all common scenario.