P.S. From one person in letter written from 2 people?

Hello,

My wife & I are currently writing wedding thank you cards, and I've run into a bit of a problem:

The majority of the messages are written from both of us, however, a fair amount of them have post scripts (P.S.) solely from my wife (mostly regarding people who were also at her wedding shower).

What is the proper way to indicate that the P.S. is solely from her, but the initial message is from the both of us?

With our names being abbreviated to J & S for the purpose of writing this, I've tried writing it out as :

Dear _______.

Thank you (etc)...

All our love and best wishes,
J and S

P.S. Extra notes here - Sara

However, something about that doesn't look right - or at least not formal.

Any help would be much appreciated! Thank you!