No, I wouldn't go through so much effort just for Halloween. But, these kids live in costumes, lol. It's like they think, why be an ordinary boy when you can be a super hero, or a pirate, or a magician, or a villain, etc.? Last year the oldest asked me to make him a Thor costume for his birthday, but he wanted the specific costume from the new movie. I told him Nana was a seamstress not a blacksmith. He settled for a penguin costume, as in The Penguin from Batman. Fortunately, I found a woman's jacket at Goodwill I was able to cut down into a swallowtail tux.
Thank you so much for that link! It's just what I needed. Having the eye and mouth holes and the increases and decreases hit the right spots is what worries me. But, really, all I need are very good measurements of the boys' faces, right? Maybe I should be thinking of this as a good time to try graphing a pattern. Gulp.