How to address a postcard to a family in Poland?

Wysyłam pocztówkę rodzinie dziewczyny (Drawski/a). Piszę się Rodzina Drawska, Rodzina Drawskich, czy Rodzina Drawscy?
Dzięki :)

Państwo Drawscy
Rodzina Drawskich

It'd be more polite to write:
Sz. Państwo
Drawscy (if known their first names or initials) R. M. Drawscy

I remember my folks addressing letters with W. P. (Wielmozna/y Pani/ie) -- is it still used?

no it isn't

But it certainly is among cultured people. I received cards this year with W.P. and Sz.P. (Polonius mentioned this above), so do not mislead people.

It would be better to say " My family and I stopped using polite forms in XXXX and we are proud of it."

I guess I have never seen a W.P. address and wouldn't know what that is if I saw one