I just took a sleeper roundtrip to NOL on the CONO 2 weeks ago.
You'll definitely get dinner southbound, as others have said it will be the express menu - chicken, veg. past, burger.
You'll also get breakfast and lunch but lunch starts soon after breakfast ends because the train is usually early in NOL.
Not sure that you'll have lunch before Jackson though.
When I went in May in Coach, we also had lunch onboard.
We had Manny as our SCA southbound and he was fabulous, made our first trip in a bedroom very special.
The Metropolitan Lounge in Chicago is very nice, quiet, and comfortable with nice amenities including restrooms - take advantage of it.
I realize that you're going to Jackson but I just have to say this.....
On the other hand, I found the Magnolia Room in NOL to be hideous.
Better than the general waiting area but almost as uncomfortable.
Straight back chairs not counting the 2 overstuffed faux leather ones.
Coffee and water, bright lights, general ugliness and it got pretty full in there too - some people went to the general area.
They can't even clean the old tape off the doors from the 'closed for remodeling' signs that had been on there.
It's like the common area in a third rate nursing home - JMO
Enjoy your trip - I love the CONO.