We always cruise 3 to a room (inside and outside rooms) and never had a problem with beds, in fact they are all very comfortable. The 3rd bed usually pulls down from the ceiling and there is a ladder of course,to get down. How often does a 10 yr old get up during the night?
The only time we had a sofa bed for the third was with a balcony room.
I'm with you, I much prefer to spend the difference on excursions etc