We boarded at Culpeper at 8:15pm on our June trip to NOL and we were not offered dinner . Do as we did and dine before you board. You will not be boarding in time for dinner.
A couple of years ago, I boarded the Crescent at CVS. When I boarded, I was very surprised to hear my SCA say "If you want dinner, go now as they'll be closing soon"! So YMMV.