I just saw "Hair" for the first time, in a top-notch local production. (For those of you in the DC area, hie thee to the Keegan theater to see it). I don't think "Let the Sunshine In" would work, now that I knowe the context of the song -- to cheer up a grief-stricken group of friends.
There must be something from "Annie," but I can't think what. There's "Oh What a Beautiful Morning," from Oklahoma. "I whistle a happy tune," from the King and I, might work, even though it's more of a song for the singers to keep up their courage. (That might be perfect for someone who is recovering).
I would DEFINITELY stay away from "Les Miz", POTO, and "Man of La Mancha" for this project.
I'm sure your thoughtful gift will cheer your teacher immensely.
Audrey, the Phantom Phanatic, who nonetheless would rather be Jean Valjean, who knew how to make lemonade out of lemons.