Hello FrankieFiveAngels. I don't know if you're aware of this, but the webmaster of this site has a main Godfather site at
http://www.jgeoff.com/godfather/ on which he has the scripts for all three movies (among other goodies). If you want to find a particular line of dialogue and you don't have the movie on hand, it's a good place to go.
In the GF3 script (at
http://www.jgeoff.com/godfather/gf3/transcript/gf3transcript.html ), near the beginning, Kay, her and Michael's children, and Kay's current husband attend the party at Michael's house to celebrate his being honoured at the church. Kay makes introductions to Don Altobello. She says to him, "It’s good to see you again. This is my husband; and this is my son…" As olivant said, this might be a bit muffled in the movie, with everything else going on; but at least you'll know where to expect it and to listen carefully

.
Two other tidbits: (1) When Kay arrives in Sicily for Anthony's operatic debut, Connie tells Kay that it's too bad Douglas (Kay's husband) couldn't come, to which Kay replies that he wanted to, "but he had a very important trial."
(2) Just before the opera, Kay receives a telegram that she reads to Michael and Andrew Hagen which says, "Here's hoping Tony sings better at Theatre Maximo than he does in the shower. Love, Douglas."
Of course, references made to "Douglas" don't say "my husband, Douglas." The viewer is just expected to infer Douglas's identity. The only reason I know for certain that Kay's husband is named Douglas is because I read the online script

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