What is the correct stationery to use when writing to someone you haven't spoken to in years, for the purpose of announcing the debut of your first novel?

Having gone to numerous panels on book promotion and publicity throughout the twenty years I was working (sort of) on my novel, I know that I am duty-bound to mimic a mosquito and buzz around everyone and anyone who could possibly have an interest in MY BOOK. Their swatting will be in vain.

Art cards? The "correspondence cards" I bought at the Metropolitan Museum of Art store? The new initial "C" cards I just purchased? The choice depends upon the recipient; I won't send the same thing to each one. Which stamps? And which address label, out of the hundreds provided by junk mailers?

What is the best way to begin? "Hello, remember me? We were in a lesbian lawyer group together twenty-three years ago. I thought you might like to know I'm having a book published. What's new with you?"

There are, of course, some people I am not planning to tell. If they discover it on their own--so be it. I have a friend who does security.