I can't seem to figure out how to load me and my wife's split-screen game on the 360. Am I missing something because when I chose continue, the game loads, but only as single player.

Log In with the Profile you started your previous game with.

Do NOT choose "continue" but "adventure" .

You should now see the two "Slots" (swap with X) for your savegames with some chapter number (like 1.5 or 1.6) -> choose split screen.
You will start at the begin of the chapter.