As half of a younger couple w/o kids that recently cruised on the Magic, I definitely endorse
DCL as a great place to cruise without kids! I really appreciated all the areas that were kept kid-free, especially Sessions, Beat Street at night, Palo, and the spa.
Then again, I found myself hanging out by the Mickey pool with a book a few times during the cruise, just watching the kids have fun - it was very cute! During the week I even met a few very friendly kids on the elevators, and it was fun to talk to them about the cruise. And we chose a secluded section of the family beach on
Castaway Cay (right next to Gil's) and had a great time.
The only place I found the children to be a little annoying was in the Walt Disney Theater - the rows are so close together, and one evening a young child was sitting on her mom's lap in the row behind me, just inches from my head, talking and eating popcorn during the entire performance. Of course, more blame rests on the parent, in that case - would it have been too hard to get the child her own seat, or to keep her quiet during the show?
Anyway, as far as dinner is concerned, our goal was to not sit with any children, so we chose the late seating. It was not possible to request "no children", but a DCL rep recommended requesting a table for 4 - thus ensuring that the our tablemates would be a party of 2, and almost certainly a couple of adults. It worked out great, and DCL paired us with another young married couple.
I doubt you would be the only couple without kids on the ship, but that probably also depends on the time of year - during the summer and other school holidays, the kid population onboard certainly grows. We loved it so much, we're planning to cruise again - hopefully next time with my parents!
April