I'd do the Keys to the Kingdom tour. I know I'm in the minotity but I didn't like Cirque de Soleil. Too much of the clowns and not enough of the other kind of acts.
Maybe not a spa - when at Disney, I try to do something that's Disney-specific, like a tour. Don't get me wrong, I love spas - but we have great ones at home, and I try to save my spending money at WDW for things I can't do anywhere else!
I've been on the Keys to the Kingdom tour and loved it! And I haven't been to La Nouba, but have been to two other Cirque shows and really enjoyed myself.
I'd add the 100 dollars to the the price that you'd normally pay for dinner and go to Victoria and Alberts. Or California Grill and watch the Fireworks from the top of the Contemporary.