If you happen to be doing an
ABD add-on package to your
Disney cruise, you can request (through
DCL) to be seated with "just your family" in the main dining rooms. (Disclaimer: You can make this request even without being on an ABD add-on, but either way, a request is never a guarantee, though they do their best.)
We made this request on our Alaskan cruise and it was granted. Not sure if ABD had any influence, but kind of think they did. We were seated by ourselves in the MDRs, but in relatively close proximity to our fellow ABDers. (A few tables apart.)
As a group of 3 adults, who were new to both DCL and ABD (and who were anticipating missing the nephews/grandkids who were not on the trip), we wanted to ensure that we could have some "low key" meals.
For us, the arrangement worked out great ... we had a blast during our excursions and special group meals with everyone else on the ABD (all families with children/tweens), but also enjoyed and appreciated our "just us" meals in the MDRs.
In terms of our group meals, as a PP stated, the arrangement switched up from meal to meal ... sometimes adults at one table, kids at another, sometimes individual families at small tables near each other, sometimes two or three families together, and once or twice all of us at one big table. Our ABD wasn't huge (I think there were maybe 20 of us, and 4-6 families total).