I’ve stayed in both Poly regular rooms and villas, and for a couple with a four year old, I would go with the villa. Is your daughter a Lilo and Stitch fan? The small Murphy bed will be the ideal size for her, and when down, it has an adorable mural of Lilo and Stitch in a hammock on the wall side. Plus it has it’s own lighting — it would be like her own little vacation sanctuary. That would leave you the sofa/chair/coffe table area as your extra living space.
For the parents, the extra shower is fabulous. It is absolutely lovely with an overhead rain shower head. I never wanted to leave it. Plus the sink in the shower-only bath provides extra getting-ready space in case another person needs to use the facilities located in the other bathroom, if you get the “drift.” (Sorry!)
With the villa, you would be guaranteed your own outdoor space (patio or balcony). The only drawback I could see is the the 20% chance of getting a dreaded Pago Pago parking lot view. I would request “Tokelau or Moorea” and hope for the best.
This is one decision where you can’t go wrong. Hope you have a great trip!
Edited to correct the info about the Murphy bed mural.