Doctor Smith and his wife Reverend Smith (assuming she is using his last name).
You could address it to Reverend and Reverend Smith. The alternative would be the Reverends Smith.
Dr. Mary Smith and Mr. James Doe
Addressing a husband and wife who are both Reverends: Reverends John & Jane Doe.
Reverend & Mrs.
What is the proper etiquette to addressing a Reverend in a letter?
Mr. and Dr. Joseph Smith (indicates the wife is the doctor)
Call her Mrs Reverend
When addressing an envelope to the wife of a doctor who is not a doctor herself then and he is Dr. John Doe, then address the envelope to her as Mrs. John Doe or Ms. (Mrs.) Jane Doe.
Dr. and Mrs.............
To;The Reverend and Mrs (Insert name)
Dear Mr. (name) and Mrs (name)
If you're addressing it to both of them - It would be: Mr & Doctor Smith OR Mr & Mrs Smith - depending on how well you know them.