Fair point on "string," though i never really encountered it, i opened up an old goldfarb book, and it's not in the index, but it looks like it is used in my old enderton "mathematical introduction to logic," so, again, fair point. I think "statement" would be a better term, maybe.
yeah I wondered about string myself, I don't see how a child could get "strings". I think they would get "letters" or "words" or even "text". That's why I just didn't get into strings, I just let them type stuff and see the result of what they were typing in the simulator which was thrilling. And when it came to teaching variables I went with int's. Even that was a long shot. I just went with "it's just a number" and I think that should be sufficient for lesson #1 :)
enderton page 107, 289, etc: http://books.google.com/books?id=dVncCl_EtUkC&printsec=front...