Addressing STDs

Hey girls! Maybe someone can help -
I'm starting to get my lists together for STDs, and can't decide how to address the envelopes. (I think this is the first of many tiny details that I am stressing over - lol)
I don't know if the STD envelopes should be:

Formal - Mr. William Jones & Ms. Kathy Smith
or
Infomal - Will Jones & Kathy Smith

What is everyone else doing?

I did it per household:

The Ramsay Family


For invites this particular might still say the same thing b/c there are mother/ father and two daughters


HTH

I am about to send out the STDs --- and they're addressed formal!


HTH