Questions on Joint Forms of Address
I wish to issue a social invitation to an Afternoon Party to a Lieutenant Commander in the Royal Australian Navy and to his wife and their (unnamed) daughters. Do I write: 'Lieutenant Commander Matthew Rowe, R.A.N., and Mrs. Rowe and family' as for an official invitations or can I write: 'Commander and Mrs. Matthew Rowe and family?' The envelope will be addressed to Mrs. M. R. Rowe at their home.
I think for the sake of convenience and brevity your suggested wording, 'Commander and Mrs Matthew Rowe and family', would be perfectly acceptable for a social invitation.
How do I address to Mr. Peter Bottomley and Baroness Bottomley?
If a joint form of written address is unavoidable, I suggest the envelope should read: Mr Peter Bottomley, MP, and Baroness Bottomley of Nettlestone, PC. Open the letter 'Dear Mr Bottomley and Baroness (or Lady if you think she prefers this style) Bottomley'.
In speech, 'Mr Bottomley', and 'Baroness/Lady Bottomley'.