People on this board have talked about programming as a gear in your brain that, to a first approximation, you have or you don't. I'm wondering if there's some well put-together resource you can direct someone with zero experience and just a web-browser to and say "if you're having fun an hour from now, you have the gear, good luck" -- maybe something on Khan academy?
(I learned to program a long time ago, and I started with BASIC program listings in my math textbook -- I don't actually know what the optimal onramps are now.)
Couldn't you lead them to guess by themselves, by asking them to guess the result of a series of expressions like:
4+2
"Hel" + "lo"
"Di" + "Caprio"
"Jack" + "Black"
"Jack" + " Black"
"ABCD" + "EFGH"
"1234" + "5678"
Maybe insert an "ABCD" + "1234" in between your last two expressions.