First, I hope this works out all right for you. The same thing happened to me once at a different property, and what actually happened was that they put me in a suite with a connecting king room--for some reason all I could see online was the king room.

If they actually involuntarily downgraded you, that stinks and it's one of the few situations that would get my ire up enough to expect meaningful compensation. For one, I think your entire stay should be free--no cash and no points. They'll still make revenue off of your on-property charges, but I think that would be a fair goodwill offer to make up for the fact that you're not getting what you booked and were looking forward to.

This property also has a "Griffin Club" level with a lounge much like a Ritz-Carlton. You could ask for complimentary access to that as compensation for the downgrade.