I'd suggest New Orleans as well, we used it for our 2013 Diamond (actually used it this year, 2014, since it's good thru March) and went during Mardi Gras.
We had a blast, we went the weekend before the BIG Mardi Gras/Fat Tuesday weekend and saw a few parades, which weren't too crowded, took a swamp/airboat tour and also went to the WWII museum, which is within walking distance from the hotel. If you aren't really into going to a Mardi Gras parade, you can still get a feel for it by just standing outside the hotel, some of the parade routes end right at Harrahs. I downloaded a parade tracker map, which showed the routes and where the parades are along the routes, it was pretty cool.
If we go back, we'd like to go through the french quarter (I'd been but hubby hasn't) and also do the Mardi Gras World tour.
If you do decide to go, just stay away from Bourbon Street, unless you want to hang out with a bunch of young, drunk kids.
IMO, it's a great town, with lots to do and plenty of awesome restaurants.