Hi Michelle,
I've been looking all over for help with writing an adoption ad and microsoft is NOT helpful.
The copy will read
"Happily married couple WISHES to adopt newborn..
the question has come up. is it...
A) Happily married couple WISHES or WISH to adopt
alternatively, adding the "A" as a qualifier...
A happily married couple WISH to adopt or WISHES to adopt.
'A . . couple . . . wishes to . . . ' is correct, but 'wish' is acceptable because it just shows that you are thinking of the couple as two people. If I were you, I wouldn't worry about it.
Ads often omit articles, so you can omit the 'a' if you want to.
Good luck with the adoption, Clive