Back to the music....as far as I'm aware (and my awareness is notoriously limited) there isn't any specific Jewish customs or music for Thanksgiving. I came up with two possible ideas for the day school program; Sukkot and Israeli kibbutz music.
Sukkot seems an appropriate connection for two reasons. First it's a Jewish harvest festival and has songs that are thematically similar to Thanksgiving, and second, I've read at least one historian who connects the Pilgrims conception/motivation for Thanksgiving with the verses in the Torah that enjoin the Hebrews to celebrate Sukkot. (You can read more about this at http://www.jewfaq.org/holiday5
The other idea is Israeli pioneer / kibbutznik songs. There are a number with harvest, or at least pioneer spirit, themes. There's a famous, and very kid friendly one called Zum Gali Gali. You can read the lyrics here: http://everything2.com/index
I meant to post this two months ago, but forgot. It's too late to help out my correspondent with her Thanksgiving program (which I hope went well) but I'd be interested to hear what other folks think. What do you all think?