Incredibly sweet, happy anniversary to you both.

100% concurring with everyone about that you just don't say anything until the FA directs her left.

If you can make it into the DFW lounge, just say you got a free CC Lounge pass, conspicuous and easily passed.

I am a bit sadistic with going as far as possible with surprises, If I was in your shoes, I'd go even farther and board with the usual Y group as if nothing changed.