Both appearances have been officially confirmed by the directors.
During one of the very beginning scenes before Moana’s father starts singing, “Where You Are” you can see a couple of villagers throw a tapestry over a laundry line. On the tapestry there are two men woven into the tapestry who resemble the directors, Ron Clements and John Musker.
After Moana finds out her people were voyagers, she races to tell her father how they can stop the darkness from taking over their island. In the scene that shows the outside of the meeting hall off to the right are two totem poles, one short and one tall. These are a reference to the directors.