When we had our pack & play in use, it very conveniently fit in the salon because the table folded up onto the bulkhead. This is an ideal location becasue the motion of the boat is best in the center and down low. A V berth area is fine if the weather is clam, but in a rough sea you could see the toddler doing some acrobatics
Our boat has a pilot berth that served well, still does actually. My wife made a mesh type Lee Cloth that kept them well contained even in some rough weather. A few pillows here and there and they slept like rocks even in the worst conditions.