For those wondering, this played out well! OP found someone to take the job. His wife bit on the prank gleefully, was actually thrilled by the idea that OP had a son he didn't know about. When the prank was revealed, she thought it was hilarious. Ultimately pretty wholesome, OP married a keeper.
This is definitely healthy marriage shit. And a marriage that is better off than at least half. Humor is a necessary ingredient to happiness and the crazier the better sometimes.
Edit: and if it wouldn't work on your marriage, one or both of you is fragile.
"I can't decide what amused her more... the effort I put into the ruse or the fact that I ended up proving her right in the process. [...She said] 'Next time you can save $100 and just assume you're wrong.'"