The selection of rooms took exactly as long as Dave had suspected. The moment one twin chose a room, the other demanded that they get the room because it was clearly the best one, and they should get equal rooms. Then different rooms were selected, and they were still somehow unequal.
In the end, Miss Molly ended up with a tape measure, checking the distance to the fridge, snack cabinets, and showers to provide a perfectly balanced set of distances between both selections, which naturally put them side by side in the center of the group of bunks.
The infant twin boys stayed next to Molly, who took a room at the end, and Dave took the far side so that nobody could escape out that end to wander the ship unattended.
They had already tried, assuming that they could find a better room if they just looked hard enough.