I saw a great, "manly," quilt made out of wool scraps that I want to make for my DH. It was called a "Hobo" quilt. It was made up of all the symbols used by hobos during the depression. The symbols were left to let other hobos know if there was a place to sleep, food served by kind hosts, dangerous place, etc. I think there's a book on it.
Unless it's really cold where he lives, I'd use a thin batting, to keep the overall weight down. You might find a skinny, wool batting to use, so the quilt stays warm, but light. I just ordered wool batting that is washable and fairly thin.
As for thread, there is a wool thread, if you can find it. It's heavier in weight and will shrink around the same rate as your quilt when washed. Otherwise, I'd just go with a strong quilting cotton. I would not use polyester because it will not shrink along with the quilt.
I think that twin size will give them plenty of "cuddle coverage."