Don't do this. Merchants in places where the crew shops will often not take them because they don't think they're real. I suspect changing them at the front desk is a real PITA for the crew. There was a discussion about this very issue on CC recently.
You do not need 1st Class Tickets. You will be able to choose reserved seats on the two websites. Take a cable lock to secure your luggage if it's going to be out of your sight. You must be able to handle your luggage onto the train.
Merchants at the ports will often refuse to take them. Even within the U.S. they are sometimes rejected because they are so out of the ordinary that people think they aren't real currency.
I have eaten at both Versailles and La Carreta when I lived in Miami, and the food at La Carreta is, indeed, very good. HOWEVER---for first-time visitors, Versailles is iconic: https://en.wikipedia.org/wiki/Versailles_(restaurant)